Ok, I don't know all the circumstances but I don't see why you should have a guilt trip about wanting someone to help pay. You didn't break your phone. Margaret and Bill are both adults and should know how to take care of other peoples' stuff. If they borrowed a phone from a friend and killed it, they'd insist on paying, right? So why is family any different?
"Family" is not another word for "people you can take advantage of and then make feel guilty", Rosie. They need to figure that out.
My mom attempted to pre-emptively guilt-trip me out of charging my sister rent when her two-week visit stretched to nearly three months.
I had already told her "I'm not going to charge you rent, but merely ask me to remember me appropriately when you can, thinking not of the extra I'm spending to keep you, but rather how much you're saving by not staying in a hotel suite with full kitchen, free phone and wireless internet."
I figure an even split of my expenses, plus the fact she (unintentionally) broke my stereo, adds up to about $800. So far she's given $620, and I'll never ask for more, nor hold it against her in other ways; as it is, she's more responsible about relatives' stuff than Mom is!
< /maximum false enthusiasm >