Having been in the position where there really wasn't $1300 lying around anywhere, and wasn't going to be anytime soon, I'd like to offer a different perspective:
1. If you have the money, pay your bills. Bottom line.
2. If you really don't have the money, or you'd have to choose between eating or paying rent and paying the cell phone companies, call them and work out a payment plan. If you're in contact with them, they won't send it to a collections agency or report it as long as you pay it off in a reasonable time frame (I'd say 6 months or so for that amount of money.)
I left a bad relationship once where all the household bills were in my name -- moved back in with my parents a state away, had no job, no assets. I ignored the bills for more than a year, but once I got my shit together and started acting like a rational adult again, I paid them all off within a month (about the same amount that you owe now). I don't have any dings on my credit report, mainly because I called the companies the second I realized I should pay them, explained the situation, and asked for some time to get things together. Every penny I earned went to those bills until they were gone (was still living with very gracious and helpful parents). Honestly it was a really great feeling once everything was paid -- running out on my debts kind of made me feel like a complete asshole, even though I technically had good reasons for it and technically only owed half the amounts in the first place.