Apologies for such a late reply - I did not get an email to advise me that you had replied.
I did nothing with the text, but it is still on my mobile from the same number that my updated allowance advisory is sent from and also other marketing material.
I did not speak to anyone about it as my account did not appear to have been affected and I assumed it was an error.. Exactly what is Fibre SIM? I was concerned at first as it said Virgin had removed allowances.