Each answering service plan includes a usage allowance. This usage allowance is the number of minutes that are included with your service plan. If the allowance is exceeded additional charges would apply.
Most clients sign up for answering service after the periodic billing cycle has been closed. If you see a “Prorate” charge, then your service had started in between a billing cycle. This results in providing you with a partial service period. In order to provide service during this partial period a prorated charge will appear on your invoice.