LinkedIn has over the years done some shady stuff. Baiting customers to share their phone contact details repeatedly is something I’ll never forget. Or, maybe they won’t let me forget, since they still nag me every now and then.
Recently, I marked my profile to only receive Job Interests in specific field/roles. I was tired of receiving invitations/offers that I would have to politely refuse.
Problem is that once you mark your yourself for “Get contacted by phone” and put your phone number in the input box. I know, my fault for clicking through without reading. There is no way to remove it or save an empty field (i.e. no way to overwrite it). They require that you provide another phone number in its place. Yet in their help pages, they erroneously suggest to just uncheck the “Contact me via phone” checkbox: https://www.linkedin.com/help/linkedin/answer/84814. Uhh, yeah that’s not how dark patterns work. 
Solution
Get a fake phone number for verification from smsreceivefree.com. Verify it through the LinkedIn page for Job Interests. Boom! Recruiters will be calling some useless phone number. Sorry for wasting your time, but I have no choice to save my sanity from cold calls.
Note: mytrashmobile.com number did not work for me.