A customer requests a refund through Payoneer Support for services almost a year old

Vlad16000

We are engaged in software development and decided to terminate cooperation with one of our clients due to inappropriate behavior, delays in payments and untimely feedback.

We handed over the entire code base (= the amount of paid work) for the paid period and informed them that we are not ready to move on.

After that the client requested a refund for 5 payments of 7-12 months old, which followed each other, arguing that he did not receive the service. We provided all screenshots with important moments of business correspondence for 6+ months and additional materials confirming that we provided services for which he paid.

I'd like to ask--
1. Has anyone encountered such unpleasant clients? How was your issue resolved?
2. Is it normal for a customer to request a refund after such a long period of time?
3. Is it adequate that the client requests a refund for payments that followed each other +- once a month and the support did not pay attention to the fact that if the client made payments consecutively - he consciously confirmed delivery for the previous payment? :#