Worst Service Ever

My line has been down for 3 months and after numerous calls no one has even phoned me back or fixed my line. I then submitted a cancellation request and when I phone to follow up I get numerous reasons as to why they can't cancelled. I finally receive an email address where I can escalate my queries to but shortly after sending my escalation email I receive a mail stating that the email could not be delivered due to the mailbox being full. This is totally unacceptable! I am told that cancellation requests / queries can only be dealt via email but the mailbox is full so how do you expect me to resolve this issue?!? This is totally unacceptable! Should my issue not be resolved shortly I will take this further.