Transfer money lost over 1 month

I opened the account and was send a letter which i thought was for my account number and sort code but it was instead for my nominated account number I wasnt given a account number or sort code for Post office so i transfered £10,000 on 26/2 thinking it was send to the post office but instead it went to my nominated account back to my current account all because post office didnt give me the write information I have lost nearly 1 month of interest and 2-3 hours making phone calls writing a letter to the post office no one got back to me all that time today i called them they said because no money went into my account my account has been closed on top of everything I think its their mistake i was not sent a letter when i opened the account stating my new account number and my new sort code which i need to make transfers too I have other online bank accounts and each one has sent me these details when i opened with them. There Customer service is bad there response back time is bad if ever and there web page for accounts is bad also not revealing your account number is very confusing I wont be using them in the future