Generally tariff allowances don't have carry overs from the prior billing period/month. Maybe they can manually add to an existing allowance period, but I don't know about that. As to being eligible, that would entirely depend on the situation. Like, if VM were responsible for you not getting the 4G signal then yes, but in the case of a setting off in your mobile/cell phone then you'd have be very persuasive when making a request of that kind.
______ Any opinions expressed by myself are entirely my own and do not represent Virgin Media in any way.