you need a burner then would need to replace it X amount of days depending on how "untraceable" you want, every few days/week usually suffices unless you're under scrutiny. Don't replenish (depending on the level of untraceable you want). Buy new from different retailers. There are some that don't do data, but depending on what you're trying to make untraceable, things like network / cell tower etc are traceable depending on where you are/local laws. You need additional level of sophistication if you looking to beat those. There are service numbers for maintenance that you can make outgoing calls for free if you have access to public payphones where you are at.
Otherwise just get a virtual sms. Much easier and straightforward if you're not doing international espionage, syndicate or adverts- guessing you would at least have a support staff for these....
