Its unlikely the freezer needs re-gassed.
My suggestion is you power the freezer off, remove any frost let the radiator at the back cool down, and then turn back on.
The most likely cause is there is a build up of frost stopping the cooling elements chilling the freezer compartment.
Another thing to check for is after a few hours the radiator\heatsink at the rear is warm, this shows the compressor is working, and coolant is being circulated.
Please let me know if you need anything clarified.
I havent heard back from you in the last few days, and just wanted to check if you still require assistance, I would appreciate it if you could rate the service received.