It is likely that one will need to supply a phone number for some service; for instance: if one aims to use the Telegram app, one will need a phone number to start the account. We do not recommend using one's real phone number for anything sensitive. One can employ the use of a burner cell phone, or cell phone number. One has two options:
- Research which local stores sell pre-paid phones with cellular plans. Generally, local supermarkets carry them. Go to one, pick up a decent model and pay in cash. Use this phone only for sensitive work, and never for personal reasons. If it is no longer needed, remove the battery and break the phone entirely by penetrating its body fully through with a sharp object in several places to ensure data erasure; and then throw it into a deep body of water, or bury it, or immolate it.
- Use a burner phone app. This option is certainly less secure, since these apps act as a front to one's actual phone number, like a mask. In this way, the app and its owners may be able to intercept one's data, link it to one's real number and provide it to third parties. We recommend the former option over this one, but we agree that one's real number should never be directly used on sensitive apps. Anyhow, if one uses the burner phone number for nothing more than authentication codes, the app owners will have no suspicions, so it is likely that your privacy is safe.