Taking out a contract is like taking out a loan, especially if your contract comes with a smart phone device. The reason for this is that the Network Service Provider will have to fund your device over the period of the contract (usually 12 months).
For this reason, a credit check will be conducted by the Network so that they are confident in signing you onto their contract (loan).
To pass a credit check your financial affairs will have to be in order. Often the requirements are:
1) You are employed (for longer than 6 months)
2) You earn over R7,500 per month,
3) You are not blacklisted or under debt review
4) You have a valid SA ID (not only a passport)
5) You have a valid SA banking account
6) You have a valid SA address (RICA)
7) You may be self-employed (however only through a company infrastructure such as a PTY (LTD)