I've reached the end of my 50 minutes. i need more time to avoid service charges. I will havwe to go to the store to talk to a service rep and review my plan. my phone battery dies every day and there are no replacement batterys available.
There is no way to add more time without risking prorated overages. If a plan change occurs in the middle of the bill cycle, you would no longer have the full 50 minutes since the plan wouldn't be on the account for the full period. As such, there would be overages as a result.
Example: The bill cycle is 30 days. You have your 50 minutes for that period. You change the plan let's say 15 days into the cycle. Those 50 minutes would drop to 25 minutes as a result.