YANBU to be annoyed someone told. YABU to be annoyed about the rollicking if the rules say don't make personal calls. Our company has the same rules; I just use my mobile (free calls etc) or ask if it's an emergency. Most companies are reasonable about this, but it costs them money for your personal business (and can have tax implications as our director just found out )
It's reasaonable for an employer to allow personal calls in case of an emergency or to confirm childcare/dependants' arrangements, but it's not unreasonable for them to ask you to clock off while you do this. (The same with going for a cigarette or snack outside of formal break times.)
YANBU to be hacked off though - I'd expect a colleague to remind me of the rules to my face.
Are you in charge of the team? If so I would completely stamp down on all personal calls, and say how sorry you are, but some (shit-faced little rodent with no life) colleague caused difficulty for you when you made one quick call, so now everyone now suffers.
At the very next personal call made in the office, I'd say very loudly to the person making the call (when they have finished of course) "you need to be careful about personal calls, some fucking backstabbing weasel one in this office reported my call the other day and I got a bollocking for it" and see who goes red and looks uncomfortable.
I used to work in an office with about 10 women, and one day got called into see the boss after lunch. She told me that one of my colleagues had told her that I spent some lunchtimes when she was out, with my feet up on the desk making personal calls
Anyone that knows me would know that I would NEVER do that... and you know, I never found out who it was!