Of course you can. VM does not deliver BB over a phone line. In that respect it is unique as an ISP. It comes over the coax connection. But if you cancel your phone line you will lose most of the substantial discount that comes with the complete package/bundle of services. So you won't save the full cost of the line rental (currently £17.99/month). You'll only find out how much you'll save when you phone to cancel. Some people have said around a £5er.
Superuser 2017/18 Use Kudos to say thanks Mark answer as "helpful" only when the problem is solved Please don't send me private messages unless I ask you to. I do not work for VM. The advice I give is based on my best understanding of VM policy and practice. You rely on it at your own risk.