Some have managed to get new customer pricing by a partner/spouse signing up for a new package but it is not without its difficulties making the transfer.
One account has to close before the new one opens. You need to return the old equipment and receive new equipment for the new package. Any email addresses linked to the old account should close within 90 days (VM does not issue new email addresses any more). You are likely to lose any existing landline number and get a new number on any new package.
It is also possible that you might get a call back from VM with a better offer if you have cancelled. But this is not guaranteed and having marketing options on in My VM is advised to allow such a call to happen.
What other providers do you have available to you? Have you priced up options with those?
You should balance the options/prices for moving to a different provider against anything you might be able to get from VM.
Having your competitor options/prices at your fingertips is advised. If you do get a call-back from VM, any offer usually only last for the duration of the call so you need to have your alternatives at hand to know if any revised VM offer is any good or not.