I work for 8 hours get paid for 7.5

As a general matter, meal breaks are not required to be compensated under federal law. Moreover, if you are on call and permitted to leave your employer's premises and to do whatever you want when no call arrives, these hours do not constitute "hours worked" for federal purposes. "All the time" raises a question of fact which may require further inquiry. Whether you can use the on-call time for your own purpose depends on the frequency of the work calls received. If you are interrupted to such an extent that you cannot conduct your regular activities, you probably cannot use the on-call time for your own purposes, and thus these hours may be compensable. You will need to discuss this situation with an attorney or your state's labor board.