Something to be aware of, If you want to port your Plusnet line number to VOIP you have to do it before the line is cancelled or the number will be lost.

If you cancel the line with Plusnet, you'll lose your phone number. If that doesn't matter, then fine.

If that does matter, then:
1. cancel the cease: now!!
2. set up an account with a VOIP provider
3. request a number port with your new VOIP provider

When that goes through - which may take a week or two - this will trigger an automatic cease of the PSTN line, and the ADSL service attached to it.