If I have a current plan and decide to purchase a phone requiring a smaller sim card do I need to purchase a new plan to activate my new phone with new sim card or can I transfer my current plan to my new phone and new sim card
Most likely. By not expressing which phone or plan you currently have, the community is somewhat handcuffed as far as suggestions go.
Still, my answer would be yes, see the document Activate My Phone .
If you tell us the make and model of your phone, and your current plan, we can advise you more accurately.
Feel free to ask any and all questions you may encounter.
if it’s a 3.0 plan you will be able to transfer that plan to the new SIM/Phone (if your currently on the GSM partner all you really need to do is punch out the smaller SIM from your current SIM (or use an adapter if moving to a phone with a larger SIM but do note this is only for the GSM based network CDMA still need new SIM when changing phones)
if you are on a 1.0/2.0 plan then you will have to pick a new 3.0 plan for the new phone (it can still take you number but all 3.0 phones need the 3.0 plans )