Confused over final Three bill 28 April 2021 at 2:05PM in Mobiles

dekaspace1

Got a PAC and it said if I use it that day my bill would be £0, took a week to use it as had to wait for a temp PAYG sim to port to and back to my other Three sim, got final bill today that mentions im £17 in credit and to ring for refund (it specifically says CREDIT) Phoned and was told no refund due but worded in a very confusing way that made no sense, checked again with Live Chat who said no refund and confusing wording about account being released or something.

Seems strange I neither owe nor due money especially after the contract was over.