For a start, in the UK you need a Radio Telephony licence in order to transmit on an ATC frequency. The minimum age for such a licence is 16 years of age.
Nope the minimum age you can start logging hours for a pilots license is 14. The kids do use the radio when they are 14. And I have had a couple of trial flights younger than that doing a bit of RT. Nobody had a problem with a "cleared takeoff".
Give the controller a good finger waving at, make him clean the fridge in the crew kitchen for a month and forget about it.