The system I used to check the masts says they're all operating as designed. There's nothing I can see to say work is ongoing. The technical support team may have access to another system that I don't.
We can never guarantee a signal inside the property because the structure may impact the strength of the signal or other devices which may be installed etc. This may not apply to you but could be something to bear in mind.
I'd definitely recommend giving the team a call again to see if they can provide you with an update. Dial 789 from the Virgin Mobile or 0345 6000 789 from any other phone.