@L_Wang88 firstly the legal position here is really quite clear, you are absolutely entitled to take a cable cutter to the wire at the boundary of your property and remove the entire lot. Now technically this is all the property of VM so what you should do is write to them and explain that you have done this and that they have a reasonable time - lets' say one month, to come and collect their property otherwise you will dispose of it. Now you won't actually get a response but you have fulfilled all of your legal responsibilities - after a month just put the whole lot in a skip!
The 'utility' argument comes up from time to time, it's actually rubbish! It now seems to have become a bit of an urban myth ie that cable broadband provision is on a par with gas or electricity or water, I suspect it's down to a misunderstanding of the regulations and laws relating to service provision.
Now if you were to simply cut the cable, could it effect your neighbours? Theoretically yes it could, however the technology involved here is actually more robust than it is sometimes given credit to - in fact legally, you are not a VM customer, you have no duty of care over their network and if their network is so fragile that it can't cope with you cutting a cable - then it really isn't your problem!
Now there is one possible drawback to this, might you ever want to be a VM customer in the future? Cutting the cable here means that they would need to repull a cable from the street cabinet to your property which they may well decide is not economic and hence mark your property as 'unserviceable'. Although this might not be an issue for you, it may well affect the resale value of the property if the new owners are unable to get VM because of your actions.