Unable to replace an old USB modem

I am using Telkom Mobile's USB modem and I've had this modem for my 3G connection for more than 4 years. My modem is damaged and I went to Telkom to buy a new one and when I requested my old type of modem I was told that I couldn't replace my damaged modem with a new one which is the same type as the old one. However what they offered me is a USB modem which costs more than R 1,000.00 and so I couldn't afford it.

As for the Telkom mobile old modems, the same as the one I have, those are only available if you purchase a new wireless modem on a contract with monthly payments of around R200.00 per month. Those customers get USB modems included in their wireless modem packages. Now that I think of this it seems like this is a way of discontinuing and discouraging prepaid customers like me from continuing with the prepaid Internet access and become a contractual customer.

I need to find out how to purchase the old modem without having to enter into a new contract to access the Internet. Please assist me I still prefer to use the D link Telkom Mobile USB modem.