You can find any Partial Month Charges in the OTHER SERVICE CHARGES AND CREDITS section of your Frontier bill.
Partial Month Charges can happen when you start or change services. If you add a new service, you are billed from the day the new service is activated. This means your next bill may include a full month of the new service, plus each day you had the new service before your billing cycle began.
Partial Month Charges are determined by taking the total monthly charge and dividing it by 30 days. This is the cost-per-day of service. Your cost-per-day is then multiplied by the number of days in the partial month.