OK, thanks for that.
The most likely, and common, cause of the problem you have, is the drain hole below the evaporator in the freezer is blocked.
You can either do a full defrost of the appliance and hope it's an ice blockage.
This would allow the ice to melt and the blockage to clear.
Roughly 36 hours, doors open, in a warm room (unplugged obviously) would sort it out.
Alternatively, unplug the appliance.
Take the rear panels inside the freezer compartment off.
Take the fan panel off.
This will expose the evaporator (mass of pipework).
Under it, you'll find the draining tray.
Fully defrost the tray and the drain hole in it.
Once water can flow down this, into the tray on top of the compressor at the bottom rear, the fault will be sorted out.
Check it out, see what you find and get back to me.
Obviously, if you cannot do the work yourself, you'll need to get someone in to do it for you.
Hope this helps