How do I get a longer coaxial cable for my hub 5?

I wish to place my newly purchased hub 5 in a different room to the connection box, hence requiring a longer cable. I understand from other posts that this requires a technician call out to fit the new cable, which is fine. However, I've had no luck getting though to Virgin Media to request this. Their bot controlled help line has proven impossible for me to navigate, and when I've used the online chat function, they've been unable to verify my account due to not having a first bill yet (or that's what they make it out to be). 

Please can anyone shed some light on how to proceed?

Thanks!