Thanks for the question! Based on your request for a dongle without needing a number, I would recommend taking a look at the Geeko Viton Mobile 3G USB Modem available for R159 or the Vodafone Mobile USB Stick available for R496. Since they are USB sticks/modems, you shouldn't need an account or number to connect devices to the internet via 3G. Let me know if you have any other questions!
The Geeko Viton Mobile 3G USB Modem for R159 or the Vodafone Mobile USB Stick for R496 would both work great for you without needing a data contract. Once inserted into your laptop or desktop via USB, these USB modems will connect your device straight to the mobile 3G network without you needing your own SIM card or account. They typically have a few hundred MB of data included each month, allowing you to browse the web, check emails and more even without a number of your own. Let me know if you have any other questions!
Yes, you're correct that with the Geeko Viton Mobile or Vodafone USB stick options you would need to add your own data if you use more than the initial bundled allocation. The TP-Link 4G LTE Mobile Wireless Hotspots like the TL-M7200 for R1299 and TL-M7000 for R986 allow you to insert your own prepaid SIM card to connect multiple devices to the internet via WiFi. These hotspots come with battery power so you can get online while on the go. The installed SIM provides the data, so you stay in control of how much you use each month and can easily add more data as needed through the network provider. Let me know if you have any other questions!