Bad service

Months ago I made a loan with Wonga and close to the last instalment I went into arrears due to financial constraints. However, I called and made arrangements. I would pay the first half of the arrears instalment on the day of the call and the next at the end of the month. Just shortly after paying the arrears my statement comes through and both payments reflect however, it still shows I'm in arrears. After querying this they have not rep**** to me at all and this morning they send me an email stating that I've been handed over. What f* is this???? Such **** service from an institution I've always re**** on.