[Russ]

Call VM CS and ask to change something on your account such as your contact number or email address.

Then ask the agent to opt you out of any marketing and it should stop within a few weeks.

The reason for asking them to change your details is so there'll be a record of your call (their systems mark the ID of anyone changing your details) and should prevent the usual case of nothing being done about your request, you calling back later to find out nothing has changed only to be told "sorry but there's no record of your call". Opting people out of marketing is often the sort of call agents like to avoid if they're trying to improve their call times/stats as they don't get to 'sink their teeth' in to it so will sometimes tell you whatever you want to hear ("I've done that for you, you shouldn't get any more junk mail from now on") just to get you off the line as quickly as they can.