Ridiculous loan interest rates

I took a loan with Wonga and paid my instalments in advance however, the interest on my loan continues to increase daily. I have contacted them several times about this issue and was told that it had been fixed, but the problem persists. This situation is extremely frustrating and concerning, as the charges do not reflect my payments. I am eager to settle the loan as soon as possible and, based on this experience, I will never take another loan with them again.