Uber Eats Spammers

Uber Eats has started sending me unsolicited sms spam. I do not, nor have I ever used them nor have I got their app on my phone. I do not know how they got my number. They did not ask my permission to start spamming me yet now when I complained that there is no OPT OUT option to stop this spam,, they say I must prove that the number is mine!!! Absolutely disgusting !!!! AND against the law too!!!