There are services that offer unlimited calling for a flat rate of around $35/month. MetroPCS is just one company like that, and they have no contracts for you to sign.
If you don’t like that, you might wish to try a pre-paid service, such as TracFone.
One way to keep tabs on cell phone usage, is to go to an office supply store and purchase a “telephone diary” or “telephone log book” that you can carry with you.
Inside, there are spaces (like in any ledger book) where you can note the time, date and length of each call you make, plus spaces to reference the number dialed, the person spoken to, and the start/end times. That little book is also a good reference tool for your CPA to use, when preparing business expenses and deductions for your corporate income taxes.