F*cken bullsh*t ****mer

I have been payimg this sh*t and my payments were refleting without any problems. Now i asked for the total amount outstanding, i paid, they requested a reciept, the bank told me they do not issue receipt, i only got my statement to prove that i paid and the money out sms. This was in December, now they coming in june saying i owe them ***! i have been requesting paid up letter from December and i have proof that i haaaaave been! I WILL NOT PAY EVEN A SINGLE CENT! Because if you were professional you would have made sure that you find my payment, so you guys have an extra 4500 that you don't know but have a client who said they paid 4500 and you tell them it doesn't reflect on your side, and you think that 4500 fell from heaven... Hay f*ck man fix this