U allocated payment after 5 days of making payment

I have been using wonga for some time but my recent experience with this company has been shocking. I took my out a loan with them that is due on 3 April 2018, I decided to settle it sooner on 9 March 2018 using the easypay payment method. I have sent them proof of payment and got confirmation from easypay that funds have been paid but 5 days later Wonga has not allocated the payment to my profile and updated their records and interest is accumulating daily on this account. I have sent numerious email and each time I get a response that they are allocating the funds. How can this take so long?