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OP I need the same thing for water and snow sports. I've been using the adapter in my spare phone...

Ive used a duo sim, you can only use one at a time but ik I need my backup phone for kayaking or other iPhone endangering stuff, I just take a nokia 6300 and am on my way. I put the iPhone in airplane mode so I do t need to turn it off either.

What is s Duo Sim??
 
Doesn't ATT drop your data if you use something like a gophone? i don't want to lose the unlimited.
 
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