Telkom wireless phone

My wireless phone battery has swollen to the extent that the phone is no longer working. I went to the Atrium Overport in Durban to enquire about a new battery and was told I must go and look at a gadget store for a battery. Could not find one. Went back again and was told I need to purchase a new wireless phone for my land-line but they don't have stock. Then I was told I could put the sim into a cell phone so I tried that and still nothing. Why should customers have to purchase a new phone because you cannot obtain a new battery for the phone. Li-ion battery.