Mazda CX-3 won't receive incoming calls

I purchased a Mazda CX-3 in December 2017 and have found I am unable to answer incoming calls, although able to send calls and return calls.

Mornington Mazda sales person and a member of the service department both handled my phone and didn't advice any problem with the model? Service department has since advised my IPhone4 is not compatible with Mazda software and I should update my phone.

Presume caveat emptor applies, but surely this should have been advised at point of sale as part of full disclosure? Surely if I can send calls the receive mode should work also?