Sorry your initial experience hasn't been great - what you describe tends to mean there's a signal issue with your kit and that needs resolving. It could be in the cabling, or your box - VM can determine this.
You've already rebooted your box, so the only other step is to check there's no reported area issues (0800 5610061) - otherwise you would be recommended to call TV Faults to report this. That's on 150 - what I suspect you've already been doing. You can also use the text message service (07533 051809) or wait on here for VM staff, but that can take upto a week.
What's concerning is that you've got these problems so soon after install - was it an engineer install or did you use the Quick Start service?
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