REFUSING TO GIVE PROOF OF PAYMENT, YET PAYMENT WAS DONE

my son's school fees account was handed over, 2 weeks ago it was paid in FULL, i sent everything to both the school and prosperitas and they both confirmed to have received it, so now i spoke to WAYVEN and i told him i was busy applying for a home loan, can they give me something in writing that states it has been paid in full, i could not hear what he was saying, all he could say was there is nothing he can do because it is now out of his hands, that's fine but payment was recieved, can they now make means that they send me a letter and update it on my credit report. They phone you more than 2 times a day when they demand payment and when it's done, they refuse with a letter to say it's been paid. I NEED SOMETHING AS PROOF THAT IT HAS BEEN PAID....THANK YOU