Now, would it make the monthly plans cheaper? Probably, but not by as much as the additional money you'd spend on the phone.
In the netherlands you can get a monthly plan for 50% of the original price if choose to go "sim-only" i.e. without a new phone. Depending on the amount of minutes you buy and the phone you'd want this can be significantly cheaper.
In the netherlands you can get a monthly plan for 50% of the original price if choose to go "sim-only" i.e. without a new phone. Depending on the amount of minutes you buy and the phone you'd want this can be significantly cheaper.