Welcome to Vodafone Community
Can you see via your online myvodafone or app what's used your credit ?
Is it possible some of your allowances had been exhausted so normal out of bundle charges were taken.
Live Chat or Customer service can log into your account and check. As a one off they may return the credit used if this was a one off and activate your BvB.
There can be an interval of an hour or two between the expiry of the old BVB and the new one taking up. So it's worth ensuring that you have mobile data switched off over that time, or you can find that the phone has done some updating, and triggered the daily OOB data charge of £2.