Bad service

I took a loan from wonga that was supposed to be payed in 3 months the first month went through. December month I asked for the banking account then I payed with EFT. January they call me saying my account has been handed over to Blake bcoz I didn't make payment for December. I sent proof of payment through their email. I then call them to check if they got the proof of payment they said yes their still busy with it, I asked them can I make payment for January they say I must wait they will call me. January ended they didn't call me or send me email. February they call me saying I'm nou owing them December and January with interests. I asked them how is that possible coz I sent proof of payment. They say it was not acceptable it was declined. They blocked my emails I can't get hold of them. When I call them I must request call back they call after days. They are very quick to place you name under blacklist