Keep your number and keep it real,mobile number porting from any network to Telkom network is quite easy and you can do it online for free if you are on prepaid number.
Just use the number you want to port and SMS PORTME#yourIDnumber#ICCID to 08611607678.
For postpaid contracts, visit your nearest Telkom store and fill out an applications form.
It takes about a day to process, but not longer than 48 hours, once you are part of the Telkom family, you will get to enjoy buffet of amazing deals!!