Refund

I'm asking for a friend so basically she bought 500 diamonds by misstake but she spent it all and refunded the money. She then had -500 diamonds and all her main heroes got freezed up ( she can't use them). She was gonna pay it but suddenly it was -1000 gems for some reason and she didn't buy anything else nor refunded. And she won't pay for 1000 gems when she only bought and refunded 500 gems so is it some kind of buy or?