Has anybody here think that crypto can work without using internet and only relies on phone data? I think I never heard such function or feature from any kind.
Transaction is just a message that can be transfered to someone with access to Internet. I guess you can broadcast signed transaction via mobile mesh networks. For example, you can use radio waves, satellite or anything else that doesn't rely on your ISP. Basically, you can send your messages offline in a truly decentralized manner. That is a real beauty of bitcoin network, it cannot be completely banned in specific country even if they cut off your cable. Found an article explaining how it works
https://bitcoinwords.github.io/cy19m5#decentralizing-bitcoins-last-mile-with-mobile-mesh-networks