No need for a lawyer.

Just contact their DPO (they are obligated to give a contact) and explain that you want to excercise your right to be forgotten (i.e. delete data)

They then gave 30 days to respond and a few months to do it. Failure to do so is an automatic infraction.

Reporting that failure to your privacy watchdog will suffice.

Provided you live in Europe of course. Otherwise the GDPR does not apply.

Telling people their rights is another legal obligation. Failure to do so is illegal.