Problem - moved to PN in June, phone & BB - still being billed by BT for phone!

[#1]

Hi all,
Placed joint order to migrate broadband and phone on 19th May. Migrated to Plusnet Fibre broadband from BT infinity on 2nd June - all okay.  Phone line went over on 16th June.  I paid for Line Rental Saver so paid line rental for the year up front.
Calling 150 shows "this service is not available from this line".
However BT Plc still think I'm their customer and are billing me £17.99 a month for phone line and calls package for June and July.
Help - how to fix and get BT to refund?

[#2]

I don't think Plusnet can help you in any way beyond confirming your service is with them.
You need to take this up with BT - have you tried posting on their forums (https://community.bt.com/)?

[#3]

Phone BT on 0800 800 150 and thrash it out with them.

[#4]

Adam created Ticket: 89036696 on your account, this covers the migration over to us and can be used as evidence should you need to provide this to BT.
You may need to look under 'Closed' questions to view this.

[#5]

Thanks, very much appreciated. (work has me away from internet last two days, so will chase BT next week).

[#6]

To answer this one for other people, the BT phone line people were all confused, I spoke to about 8 departments starting with "cancellation" and then "migrations" and eventually "order management" as the computer basically said "no".  I did threaten having to go to Ofcom a few times, but they were all lost and could see the problem but no idea how to fix.
So on thinkbroadband I gained the BT Care website link, and reported the issue last Thursday into the web form. I had a phone call from BT Care this morning (on a Sunday!) who have resolved the issue, organised a credit and final bill to be sent from accounts in the next few weeks. Ten mins later I had the "sorry you're leaving" email from BT for the phone line, dated Monday.
So fingers crossed all resolved - weird one.