Be careful when you want to cancel your contact withe RAIN

Please people be careful when you want to cancel your Rain contract. On cancel my Rain contract they inform me to pay a last fee, which i did and ask for proof of payment and cancelling of the contract, they Rain supply me with a Ref no ***, Year's later i receive a notification from Nudebt that i owe Rain R475.00. Rain never contact me about this payment. My question is way do they not recognize there own Ref no, which they supp**** after my last payment and cancelling of my contact. The reason i cancel my contact is there is a constant problem in receiving WiFi connection. If you want to cancel your contract, make sure you get it on E-Mail or in written form. Because you will have a additional bill years later. Think there must be a lot off people having the same problem.