Hi @FJ2, thanks for your post although I'm sorry to hear of your concerns raised regarding the credit issue.
Do you have data allowance as part of your package please, is it possible that you have gone over this and therefore incurred usage charges?
Can you please also check your Virgin Mobile account, to see if you have a spending cap on because if so and you've gone over this, this might explain why things aren't working properly for you.
Please let me know and we can take things from there.
Many thanks
Tom_W