Hello all, ok I work in a model shop - just so your aware - I wont name it and its hopefully nothing to do with this!
Firstly if your radio is faulty, and you bring it back to a model shop the shop should at least test it in front of you, or let you show them the fault.
We would then swap parts around to find and then be certain of the dodgy component, in your case the tx! Its rare for a new (how old is it) tx to not work, its the servos and rx that have the hardest life - lets face it!
But nowadays every model shop does get stock that simply does not work - even futaba, ive bought a dead futaba rx before, stuff these days is made to a price, 1 or 2 in every couple hundred is almost normal and acceptable to manufacturers.
But when you buy it, it should do what it says on the tin!
Yours very likely clearly looks as new and you have proof of purchase, the store should at least offer you a replacement tx that binds fully with your rx or offer you a full set, assuming even that you wish to keep the servos installed in the model?
If your not happy with that, offer you a refund and then they send the tamco radio back to supplier.
The fact that the RC has been fitted has no bearing, that's how you know it does not work.
Bit like buying a TV, you have to unpack it, and plug it in, that's when you find out it does not work- simple!
So, my advice like the above chaps, is take it back, ask them to check it, under its warranty, if faulty replace it. Don't go in all "trading standards guns blazing", if they say no! Ask them why they are saying this based on the sale of goods act, if they have any sense they will help you.
If not - they are letting the few remaining uk model shops down!