The passing of the Electronic Communications and Transactions Act ("the Act") had the result that it is now possible to contract by means of data messages, which includes e-mails and sms's or Whatsapp's.  This was confirmed in the case of Jaftha v Ezemvelo KZN Wildlife, where the court held that a contract of employment was entered into even though it was done informally via sms.  

The Act however provides for certain exceptions and the two most noteworthy ones are the purchase of immovable property and drafting of a will.  A deed of sale must be in writing and signed by all parties.  It is also important to note that any amendment, i.e. an extension of the date by which to obtain a loan, must be in writing and signed by both parties as well.  

The moral of the story is that one must be alive to the consequences of cellphone and e-mail chats and it is always best to consult an attorney when purchasing property or drafting a will.