O.K - I had the some "cons" as you did about phones Soul, and I think we probably have the same opinions on a few things. However my darling daddy (and sucker) bought his darling grandaughter one when she was 13. I wasn't too pleased...

BUT

she is 15 now and these are the advantages I have found -

She can remind me about school events I have forgotten about.
- She ALWAYS lets me know if she will be late home (public trans issues etc).
- Sometimes she is quiet and unresponsive, but we can have lovely txt conversations on her school lunchbreaks.
- She can plan outings at a moments notice, and can tell me how she is getting somewhere and what time she will be home (a requiste before she goes anywhere)
- She knows she can get hold of me wherever she is for help. There have been hassles getting home from school sometimes and it has helped, (her friends will often txt their parent that they will be getting a lift home with me too)
- She learns to budget her credit, it's also a great pressie for the grandparents - it's hard to find something they like when they get older. A $20 credit can last for ages if you don't automatically top it up for them. Belle might get $15 credit here or there for good school performance, but it's not written in stone.

We have rules like - mobile in the kitchen by 10pm each night etc.

Just because Belle has a phone doesn't mean she can do as she pleases, believe me, I always know where she is - phone or not. She could have carried on about the rules, but she chose to be grown up about it, and wants part time job so she can upgrade it.
Like it or not, phones are now a huge part of a teens social network, I know here gf's have been a great txt support to her in whatever drama happens (!).
If you have brought up this girl with your values, trust in yourself that she will reflect that and be responsible. A mobile phone won't change your daughter.

xoxoxoxo