My O2 sim is blocked without a valid reason

my o2 sim is blocked and it is saying registration error. I did online registration, my sim was activated. now after 15 days it is blocked now. i can see network bar on my mobile screen but can not call, receive, text or do anything. i inserted the sim in other mobile but still the same. i went to many o2 shop but the told me thay can not help with registration issue. i am suffering since 1 week. I am out of any valid contact with a blocked sim. is there any one who can help me. otherwise i have to switch number that is very unfortunate.

my number is 017688135846

name sunjida afrin