E: Package 'cdbs' has no installation candidate

For diagnostic purposes please provide the output that you receive for the commands

uname -a
lsb_release -crid
apt-cache policy

(Remark: from Bionic onwards cdbs is in the universe repository)

If you have become root you don't need sudo. Are you logging in to Ubuntu as root?

Seems to be in the proposed repo
https://launchpad.net/ubuntu/bionic/amd64/kannel/1.4.4-5

root@sms:~# uname -a
Linux sms 4.4.0-116-generic #140-Ubuntu SMP Mon Feb 12 21:23:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
root@sms:~# apt-cache policy
Package files:
 100 /var/lib/dpkg/status
     release a=now
Pinned packages:
root@sms:~# lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

It seems that the package management system (for installing and updating software packages) is completely misconfigured. Your output does not show any repository server listed (besides your local cache directory).

What is the output of the commands

cat -n /etc/apt/sources.list
ls -l /etc/apt/sources.list.d/*.list

cat -n /etc/apt/sources.list
 output:

root@sms:~# cat -n /etc/apt/sources.list
     1
     2 #------------------------------------------------------------------------------#
     3 # OFFICIAL UBUNTU REPOS #
     4 #------------------------------------------------------------------------------#
     5
     6
     7 ###### Ubuntu Main Repos
     8 deb http://us.archive.ubuntu.com/ubuntu/ xenial main
     9 deb-src http://us.archive.ubuntu.com/ubuntu/ xenial main
    10
    11 ###### Ubuntu Update Repos
    12 deb http://us.archive.ubuntu.com/ubuntu/ xenial-security main
    13 deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-security main
    14
    15
    16
    17
root@sms:~#

ls -l /etc/apt/sources.list.d/*.list
Output:

root@sms:~# ls -l /etc/apt/sources.list.d/*.list
-rw-r--r-- 1 root root 79 Jun 12 17:30 /etc/apt/sources.list.d/fossfreedom-ubuntu-packagefixes-xenial.list
-rw-r--r-- 1 root root 73 Jun 12 17:30 /etc/apt/sources.list.d/gnome3-team-ubuntu-gnome3-xenial.list
-rw-r--r-- 1 root root 75 Jun 12 17:30 /etc/apt/sources.list.d/nilarimogard-ubuntu-webupd8-xenial.list
-rw-r--r-- 1 root root 74 Jun 12 17:30 /etc/apt/sources.list.d/tldm217-ubuntu-tahutek_net-xenial.list
-rw-r--r-- 1 root root 0 Jun 12 11:23 /etc/apt/sources.list.d/ubuntu-audio-dev-ubuntu-ppa-xenial.list
-rw-r--r-- 1 root root 76 Jun 12 17:30 /etc/apt/sources.list.d/videolan-ubuntu-stable-daily-xenial.list
-rw-r--r-- 1 root root 71 Jun 12 17:30 /etc/apt/sources.list.d/webupd8team-ubuntu-java-xenial.list
-rw-r--r-- 1 root root 80 Jun 12 17:30 /etc/apt/sources.list.d/webupd8team-ubuntu-y-ppa-manager-xenial.list
root@sms:~#

Your sources.list file is insufficient.

You need at least to enable the universe repository, and should also enable xenial-updates.

Then run the commands

sudo apt-get update
apt-cache policy kannel cdbs

and report what the results are.

root@sms:~# cat -n /etc/apt/sources.list
     1
     2 deb http://us.archive.ubuntu.com/ubuntu/ xenial main restricted
     3 deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
     4 deb http://us.archive.ubuntu.com/ubuntu/ xenial universe
     5 deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates universe
     6 deb http://us.archive.ubuntu.com/ubuntu/ xenial multiverse
     7 deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
     8 deb http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
     9 deb http://security.ubuntu.com/ubuntu xenial-security main restricted
    10 deb http://security.ubuntu.com/ubuntu xenial-security universe
    11 deb http://security.ubuntu.com/ubuntu xenial-security multiverse
root@sms:~# ls -l /etc/apt/sources.list.d/*.list
-rw-r--r-- 1 root root 79 Jun 13 10:41 /etc/apt/sources.list.d/fossfreedom-ubuntu-packagefixes-xenial.list
-rw-r--r-- 1 root root 73 Jun 13 10:41 /etc/apt/sources.list.d/gnome3-team-ubuntu-gnome3-xenial.list
-rw-r--r-- 1 root root 75 Jun 13 10:41 /etc/apt/sources.list.d/nilarimogard-ubuntu-webupd8-xenial.list
-rw-r--r-- 1 root root 74 Jun 13 10:41 /etc/apt/sources.list.d/tldm217-ubuntu-tahutek_net-xenial.list
-rw-r--r-- 1 root root 0 Jun 12 11:23 /etc/apt/sources.list.d/ubuntu-audio-dev-ubuntu-ppa-xenial.list
-rw-r--r-- 1 root root 76 Jun 13 10:41 /etc/apt/sources.list.d/videolan-ubuntu-stable-daily-xenial.list
-rw-r--r-- 1 root root 71 Jun 13 10:41 /etc/apt/sources.list.d/webupd8team-ubuntu-java-xenial.list
-rw-r--r-- 1 root root 80 Jun 13 10:41 /etc/apt/sources.list.d/webupd8team-ubuntu-y-ppa-manager-xenial.list
root@sms:~#

root@sms:~# sudo apt-get update
Err:1 http://security.ubuntu.com/ubuntu xenial-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Err:2 http://us.archive.ubuntu.com/ubuntu xenial InRelease
  Temporary failure resolving 'us.archive.ubuntu.com'
Err:3 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease
  Temporary failure resolving 'us.archive.ubuntu.com'
Err:4 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease
  Temporary failure resolving 'us.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial/InRelease Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease Temporary failure resolving 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.

root@sms:~# apt-cache policy kannel cdbs
kannel:
  Installed: 1.4.4-2build1
  Candidate: 1.4.4-2build1
  Version table:
 *** 1.4.4-2build1 100
        100 /var/lib/dpkg/status
cdbs:
  Installed: (none)
  Candidate: (none)
  Version table:
root@sms:~#

During running the command "sudo apt-get update" you had a network problem.
Try solving the network problem and re-run the command until you have no network errors any more.
Then repeat the apt-cache command.