I let a bill become way past due. Now things are better BUT will they let me cont. the monthly payments?

I'm a single mom working & going to school full time. My income was cut by more then half BUT things have changed and I can afford to pay the monthly payments again. Will they let me or will they only accept the whole amount owned now that it is sooo past due?? What are my options if I have any? Thanks for any advice :)