Frustrating

I sent money 12 December on my account and the transfer was successful i tried last Friday and keeps telling im using wrong recipient and i tried with different account and they say wrong account number i can't seem to get anywhere with the problem and now they say I've been changing recipients like i don't understand.. I have a sick child to assist and the finances are for her.

They are really unreliable and not fair cause same transaction was made don't understand where they got the wrong name from as i never updated details since my last update before transaction in December