I want my cell phone to have internet even when there is no WI-FI. How can I do it? What do you recommend? Preferably a proven method.

First of all, you should contact the cellular company you use. If this does not give any result, then you should think about another option. For example, you can try to buy mobile proxy 4g / 5g. This will give you the opportunity to connect to the Internet at any time. This topic is described more precisely and clearly at https://floppydata.com/proxy-type/mobile-proxy/. I think this will be the solution to your problem.