RC Helicopter interference with another helicopter?

Hi, myself and my Dad got an RC helicopter each (same model) -
http://www.trademe.co.nz/toys-models/radio-control/helicopters/auction-424744533.htm
Anyway, my mum asked the shop keeper for a helicopter model that if we bought two of we could change the channels so we wouldnt have the issue of interfering with each others frequency and flying one-anothers' helicopter.
There's no buttons or switches on the controller, nor the helicopter, that I can see.
Was the shop keeper incorrect when informing us we could use them near each other without picking up each other's frequency?
Thank you

Sadly, Real full 3D control!,Infrared Control , Is basically a system that is extremely susceptible to interference! specially if you have to of them on the air at the same time! the only good news that I can give you is that for as long you have enough distance from one an other! I will say about 15 feet and you don't point your remote to the other aircraft you will be in the safe side. Understanding that You don't have in any way shape or form a physical way to modify the Transmitter or Receiver, that is your only option! You very much get exactly what you pay for! Never the less get out there and Have fun!