Free 1GB data on Prepaid

So my dad is on vodacom prepaid for years.... I mean like years his simcard is so old I think its a 16k sim still.

Anyways he asked me what does the sms he got mean... The sms said use your Free 1GB internet bundle on the internet by downloading apps ect ect....

When I checked he got 1GB free data that is expiring on the end of January 2014..... How can I get this data reward? :D As you can see my dad bearly even recharge or anything. He just receives calls on it mostly...