I spoke with tech support this morning on an unrelated issue and asked about 5G requirements. The rep said it has to be one of the unlimited plans.I hope the guy you spoke to was right about not having to change plans and please keep us posted. What plan do you currently have? My brother also called and they even told him that the plan had to be changed, just saying.
She also confirmed that a user can use their existing nano-SIM and utilize 5G (with an unlimited plan).