Unclaimed Debt

I worked on a project that wasn't mine; I was a representative in this project. In this project, I sold people certain certificates they pre-ordered, and people paid me when they came to collect the certificate. I also ordered a certificate for myself, and because I distributed the certificates to people, I didn't pay for my own certificate. Then they took all the money I received for the certificates from me. Later, I tried to ask them if they would agree to waive the payment for my certificate as a token of appreciation for the work I did for them, but they didn't respond to me on this. I asked them several times via email again and again, and they don't answer me on this, although I know they saw my question several times (because they answered me on other things I asked them in the same email). Should I continue to pursue them to pay them (until they answer me by email), or not? I hope this was clear enough.

Hello,
After you have notified them, if they do not demand the money, you do not need to pay.