Having issue with Zain telecom

Dear Expats,

The issue goes long way back when COVID started, i ordered a 5G device from Zain using there online shop. It was portable huwai device. But before there delivery i found out with research that this portable device's performance is not very good. So by the time someone from zain contacted me about the delivery of zain device. I asked him if i can change the order into bigger home device. He said yes you can cancel this order and place a new one using online shop and email all the details to specific email address. They will cancel and refund your amoun. I did exactly as he told me and now basically ordered two devices. The second device came to me as ordered and i started using it but never got the refund. But after 3 months, I started receiving calls that i have to pay for a device (that i never got) i told them guys it was canceled long time ago and you have to refund me my money. They never did that and kept calling every month. I raised the issue on CITC website and upon doing that i instantly got my money back. But its been now years I'm getting call from some collection office about this 1400 riyals. I even visited the Zain branch 4 times. They always send me back saying it is resolved. But it was never resolved and still going on. I hate to receive there calls i even fought with them but no use... please tell me what to do and how to resolve it for once and all... thanks