The salesmen at Currys, PC World and the like frankly don't have a clue, never found one that had a clue what they were talking about. When Freesat first launched Currys insisted that you had to have a new special dish installed and that your existing sky dish wouldn't work. They even refused to sell the Foxsat without a dish install being paid for (Numpties )
Go back to the shop, assuming they are using an English postcode get the salesman to disconnect the second cable (turn off the box first), carry out a reset and then ask them to tune to BBC 2 HD (102) and press record. Now tune to ITV HD (119) and press record again. Now tune to BBC1 HD (108) and live pause it. Release the live pause and wait for a few minutes. Now stop one of the two recordings and press record on 108, you will then be able to record 108 from the time you started watching it (from the time shift buffer ). Now display the media list to show you have three recordings and politely ask how did that work then