Wonga's collections department is the worst!

I am paying off a loan that i took in July and was due in September. Each time that i am making a payment i make it a point that i send your collections department an email notifiying them of such payment. They are the sloppiest and laziest bunch of people i have ever seen! I would not have minded if it was not affecting me financially but now it is and i am livid! On Sunday i checked the account and saw that i was left with an outstanding balance of 675. Being mindful of the minute interest increasei decided to put in 680 and promptly send an email to your collections department so that my account could be cleared as soon as possible. I had hoped it would have been done by end of business on Monday but today its Tuesday night and it still has not been cleared. The problem is that now the amount is 681.47! So does that mean i have to send yet another ammount because you could not do your efficiently! I am literally paying you more for not doing your jobs. My account email is ***. Please clear my account because i want to close it. You have the worst service ever!