When minutes run out before time, then what?

[displacedyankee]

I have $45 in my account. My $15 / 300 minute plan expires in 2 days, and I am down to 9 minutes. What happens if my minutes run out today? Can I still make calls before my $15 plan renews in 2 days? If so, what will I be charged:  by the minute, or daily? I have been all over and I cannot get anything clear on this situation.

[LENNYEDGE]

by the minute. its best re up no matter what online or store versus by the minute. could get ridiculous if wait til run out.