FNB Sucks

So I have a personal loan with FNB.. In January i emailed them to have a payment arrangement from February to end of May as i was on maternity leave and had zero maternity benefits from work and had to rely on UIF alone. My usual repayment amount was R1333 and some cents. They reduced the repayment amount to 590 while I was on Maternity leave. The arrangement was that for 4 months I would pay 590 and when I started work again I would then pay a new amount of plus minus R1800 for 3 months to make up the loss of the previous months. Which I agreed to. Every month I would get sms's stating that my account is in arrears.. I have tried phoning multiple times to sort this out, but the loan department simply does not answer phones! So just a week after I started work again a lady from FNB phoned me stating that my acc is in arrears and I have to settle the amount that same day. So I told her that I was not going to settle the amount as I had a payment arrangement with them (i have emails and documents to prove it). She then checked her system and said yes I can see you have a payment arrangement but she cannot see what the new repayment amount would be, so I told her that in the email it stated it would roughly be R1800.. So this morning, after payday i get a msg from FNB stating that they will debit all the money outstanding, which they did! They debited my account twice!! R1333 x 2! This could have all been prevented if the people at fnb actually did their job. That second payment should be reversed immediately!!