I can't follow what phones you are using now.
If you have 10 GB of data or more:
And you have phones out of contract, you can get your line charge down to $15/month
If you have phones active on the Edge plan, you will have the line chart of $15/month
If you have old phones but they are still in contract, that is $40/month
For the first option, where you have old phones out of contract, you need to add the month to month feature to your line (does not happen automatically which is pretty slimy), to get the $15/month.