When your contract expires you should be able to start a new contract, but without Digital Voice. This would be a broadband only one.
Meanwhile you can change your calling plan to remove any call packages, and revert to PAYG.
The question is also, were you out of contract before you were move to DV, or did you recontract and then were forced to have DV?
If you were out of contract, and DV was forced upon you, then the phone part of your contract would remain the same, and if you did not have a Smart Hub 2, then BT should have supplied one FOC, as they were altering your contract.
There are people on legacy ADSL contracts which include PAYG calls and even free weekend calls, without any extra charges. Its only if they chose to renew their contract that they are going to face an increase in charges due to a forced move to FTTC/FTTP, and associated charges for a phone service if required, and also the extra yearly increase in charges.