SAFAIR poor online checkin system

Not sure what is going on with Safair. My dad uses clutches, so I usually set an alarm for the 24 hour mark before a flight to ensure we get the furthest seat forward. This time however I was surprised to note that Safair had already selected the seats for us. Is the 19th row! When I tried to modify it, I was being charged for this change. This was never the case prior, and it really annoys me that this is the case.