It will probably be on Tuesday given that Sunday is not considered a working day. The courier guys will probably call you before hand to agree with you as to what time would be convenient for the delivery. The following is an extract from Vodacom's "How to upgrade" webpage.
Upgrade online now and get FREE next-day delivery!
Simply register or log in to My Vodacom to check your next upgrade date.
Upgrade from month 22 of your contract and get a brand new cellphone absolutely FREE, depending on your price plan and the cellphone you choose. We will also make you smile with FREE next-day delivery to your door if you confirm your order before midday, depending on stock availability.
Where can I upgrade my Vodacom Contract?