Migrating from BT to Plusnet - final bill question

Swipe

This is why getting billed quarterly in advance doesn't work. They did exactly the same with my elderly parents i.e. took 3 months line rental and BB in advance 4 days before their switch date. And then tried to tell them they were owed just £10 refund instead of £80. It took me 4 phone calls pretending to be my dad to get back what they were owed. There's no way my parents could understand the way the bill was laid out, it was so confusing. For that reason alone I'd NEVER go back to BT.

All I can advise the OP is to go through that final bill with a fine tooth comb.