Reporting part-time earnings while on benefits

I picked up part-time shifts as a bank teller and I am confused about how to report them. I have been trying to stay organised about it. Pay posts on a different day from when I work. Who can I ask without risking my claim?

Keep everything in writing and save the confirmation numbers. It saved me later.

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.