This is in the wrong section, in order to get the attention of the Forum Staff which can take a few days, It should be in 'Manage your account'
It's frustrating to have to keep calling and not see the issue resolved. Here are some steps you can take to try to resolve the issue:
Keep a record of all the times you've called and the names of the people you spoke with. Make sure you have notes on what was discussed and what was promised.
When you speak to the manager, explain the situation calmly and clearly. Be specific about the problem and the steps you've taken so far to try to resolve it. Ask for a specific resolution and a timeline for when it will be implemented.
If you don't receive a call back or the issue is not resolved to your satisfaction, consider escalating your complaint to a higher level of management or filing a complaint with the regulator Ofcom. You can find more information about how to do this on their website.
If you have a social media account, you can also try reaching out to Virgin Media on their official accounts. Companies are often very responsive on social media, and it may be a way to get their attention and get the issue resolved.
Regarding your question about whether this is normal behaviour, it's hard to say. Billing errors can happen with any company, but it's important for them to take responsibility and take steps to resolve the issue quickly and efficiently. If you feel that your concerns are not being taken seriously, or if you feel that you're being given the runaround, it's important to escalate the issue until you get a satisfactory resolution.
I hope this helps, and I wish you the best of luck in getting the issue resolved.