cannot uninstall Avira Antivirus [Solved]

Instructions for manual uninstallation

https://www.avira.com/en/support-for-home-knowledgebase-detail/kbid/902

How To Remove Numbers From The Blocked List

Head to Settings > Applications > Call. Next, click on All Calls > Auto Reject > Reject list. 

Here, you will be able to add or delete numbers on this list. You can remove a number from the reject list by simply unchecking the number(s) of your choice.