I've just got a "big bundle" sim only for my teenager. Works great, 1gb data, enough texts. I only top up when he goes away and needs mobile data.
I've topped up a couple of times now and there is a balance of £30. If I keep topping up I will build daft amounts of credit, and I might as well get a £5/month contract sim. Can I buy extra data or something, or does that money just sit there never to be used?
I had similar on 02 and that lets me buy extra "boosts" with my credit, so when I had a balance I bought a boost rather than top up again.
I did ask on the chat service but they couldn't help, told me to phone. Can't be doing with the phone line.
You use the balance to pay for any chargeable usage not covered by the rewards. On the Big Data and Texts tariff that includes - all calls, all picture messages, data above the reward amount, texts and data in a month without any rewards (not topped up the month before).
Data use outside of the reward is £1 per 100MB per day, for example.
I used to top up on average 2 out of 3 months - two months with rewards then one without. Since I don't use my personal phone away from wifi most of the week I turned mobile data off except for the weekends.