7 to 8 cents per minute is a competitive rate which you can get without signing volume commitments, and without committing to use bundled services. Sprint's Unlimited Weekend calling plan is a good example of this. To justify this expense, you need to spend at least 4 hours per month making long distance calls on weekends. If you don't anticipate calling this much, you're better off going with a simple plan where you pay a flat rate per minute regardless of time period. There is a dirty little secret in the telecom industry.
Carriers do all of their billing by computer.
Computers can process mind-numbingly complex sets of rules for billing services whereas most consumers, unless gifted with a stratospheric IQ, are unable to comprehend the complexity of the billing scheme. They design calling plans with the expectation that you will not understand the fine print, and therefore, will wind up using more service than you thought you did. This system works beautifully. Most consumers don't comprehend what is in the phone bill, and unless they are outrageously ripped off, pay the bill without question. To figure out which program is best for you, you'll need to understand how your employees use the phone.