Product: Debt or credit management

There was a rental debt with National Credit Systems. Me and the other person who they put the rental debt on first spoke to them on the phone on XX/XX/XXXX at XXXXXXXX XXXX, the call was XXXX minutes long ( I recorded every single phone call with them for my protection and so that way they could not claim anything false. ) upon getting on the phone me and my mother were super nice we just wanted to pay our debt and get it removed off of our credit report. We spoke to XXXX XXXX who was assigned to help us. We told him we would pay our debt for a pay to delete. He talked to us like we were incompetent and kept cutting us off but we just wanted to move on with this situation. He told us that when we paid we would get a receipt and a letter stating that the debt was paid in full and that they would send that information to the credit bureaus. He told us to wait XXXX hours and the receipt would show up on the portal the next day. The original balance was XXXX but we settled for XXXX. We paid on XXXX separate cards XXXX $ on the first card and XXXX $ on the second one.Once we got off the phone we received an email that gave us a login to their portal which we were supposed to login to on Saturday and see the receipt. When we logged in the next day there was no receipt and it showed as if we only paid half ( XXXX $ ) of the balance.We decided to try and wait until Monday so they could update the information. We called back on Monday and spoke to XXXX again but this time he was super rude and seemed frustrated with us. We told him we received no receipt for our payment and that the payment showed that we only made half of the payment so where did the money go ( the other half of the payment which was XXXX $ ). All he did was simply tell us how to login the portal which we already had instructions for and kept telling us that we should see a receipt which we did not. Eventually we just got off the phone and decided we would try to find the receipt ourselves due to him not being helpful. While me and my mother were trying to do that he called us at XXXX on XX/XX/XXXX trying to collect money for the debt we already paid! when I answered the phone he asked if he was speaking with me and I said yes and he proceeds to say that we owed a certain amount to national credit systems. Me and my mother were confused because we already paid him so we called him out on it and reminded him that we were trying to find receipt so why is he calling us for more money. He proceeded to say that he remembered us which clearly he didn't because he asked for more money and we were lucky that he called back because we clearly needed his help.We asked him if he even closed our account and he said yes but that was clearly a lie because he called us trying to collect money again. Eventually he went over to his supervisor and said that he would send us the receipt which we were supposed to been had and a letter stating that the debt was satisfied. When we checked with the credit bureaus they updated the balance to an incorrect amount and it is still on our credit history. My concern is that they could never come up with a receipt and even after they accepted the settlement was paid they called me back after several phone calls trying to collect a debt, how do I know they will not try and contact me again trying to collect money. They would not provide a pay to delete letter which we agreed on and even on the letter they provided that states that the debt is paid is satisfied it still shows a balance.