Hi Marilyn,
assuming the motor is still working, the most likely cause is ice build up on the fan which blows cold air from the freezer into the fridge.
Switch it off and let it defrost with the door open for several hours, at least overnight. Ensure it has completely defrosted before switching back on.
If you want to check, and it is like mine, then...
Switch it off from the mains. Remove the draws from the freezer. There is a plastic panel on the back wall secured by 4 screws. Removing this allows you to insert your hand at the top of the revealed opening. You should feel the fan. If it is frozen solid then that is the problem. Defrost it to cure the problem. But make sure it has completely defrosted and has dried before you switch it back on.
1st time this happened the call out guy said it happens a lot and that 'frost free' freezers needed defrosting once a year as a prevention.
Defrosting is a good check before calling anyone out and a lot cheaper too.
good luck
Brian Hunter, June 2008