Yes you can pay your regular monthly bill (current charges) at the same time you pay your payment arrangement amount. Your due date for your current charges may be different than the due date on your payment arrangement. You will need to add your current charges and your payment arrangement amount to get the total to pay both at the same time. Be sure that both payments are made prior to their respective due dates.
Current charges of $100 due December 15th. Payment Arrangement charges of $46 are due on December 21st. To pay both amounts at the same time, a payment of $146 would need to be paid by December 15th. The other option would be to make two payments, on their respective due dates.