看到我的账户有余额，我松了一口气。

I was relieved to see from my statement that my account was in ___credit.

我一周后再给你打电话，因为我的手机话费不够了。

I will talk to you on the phone in a week's time as I don't have enough ___credit.

我的手机话费用完了。

My phone has run out of ___credit.