someone is using my AS number

On 12 June 2019 6:05:58 pm GMT+02:00, Philip Lavine via NANOG

What is the procedure to have another party to cease and desist
in using my AS number?

Here is what I got from BGPMon- MY AS is 15053

Detected new prefix:
ASpath: 394256 174 702 25213 25213 25213 15001 15053

Seems the issue was on AS25213 side. They don't provide transit
to AS15001 at all.