Migrate phone service only, to VoIP provider?

Unfortunately, as you have found out, doing this transfer will result in having a new 18 month contract issued.  However you can still setup a new VoIP service, albeit with a different number, and port your VM number at a later date.  Depending on your VM phone service, you could possibly call divert the VM phone to your new VoIP number?
I would highly recommend moving to VoIP btw.

Hey J2R, thank you for reaching out and a warm welcome to the community, we are happy to answer your questions about migrations. 

As mentioned above this is true. Normally we send an adapter out for this.

Have you got one of these?

This must be new. I moved my phone service from VM to a VOIP provider over a year ago. I never heard anything from VM. It was only the most basic phone service as it was only used for incoming calls. 

I can understand why though because VM only use the phone service to bind customers to the broadband. It would be interesting to have a legal opinion on this because you are still paying the same whether you use the line or not. 

Services are bundled, & these bundles attract various discounts. The phone line attracts the biggest discount, so removing it affects the pricing of everything else. The only advantage you have is that VoIP lines don’t carry a line rental charge. Do the sums, & if it is worth it go ahead.

While cost-of-living pressures continue, bundle options are of decreasing interest to many people, especially when they include things like an unwanted landline.

That said, when I put my own address details into VM recently to look at pricing, I could not generate any bundle options at all which showed landline as being included. New VM cabinets have been in place for a long time in my area. I wonder if the lack of a landline option signals a changeover period for VM before a true VOIP solution is implemented.

It would be great if VM would give you the credentials for their VoIP service, rather than require an analogue phone to be plugged into the VM hub. They would still ditch the analogue line, but it would open up a world of possibilities to use modern VoIP handsets.

I looked at porting the number out a while ago now. I gave up on the idea when I found how draconian the VM policies and pricing structure are. Not many companies can get away with increasing the cost to then consumer when actually supplying fewer services.

OK, given the hassle surrounding this, I've decided to leave Virgin Media for PlusNet. I don't really need to keep the same landline number, it was just a bit more convenient. I'll go instead with the one issued by the VoIP provider. I'm going to save myself over £100 per month, for a faster broadband service (900Mbps), albeit without TV or phone. But I don't really watch much 'live' TV these days and can easily get by with iPlayer, ITVX, etc., and the phone side of things will now be handled by Andrews and Arnold, the VoIP provider.

Plus 1 for A&A. I found them totally professional. And not expensive either.