Oh dear. If you have a VM mobile phone calls to the short code service number 789 are free. That is made clear in all VM mobile literature and on the Mobile web pages.
There is no e-mail address for contacting VM mobile. They want to do all their business by phone. The Forum cannot deal with account questions because of data protection limitations.
Welcome to the Forum - though you'll be disappointed by the advice.
Superuser 2016/17 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.