Not sure if I understand this correct. If your home loan has been securitized it means it's now owned by a SPV. And because there is no legal contract between you and the SPV there is no monetary obligation to neither the bank nor this SPV?
Yes. You entered into a contract with the bank when you bought your house. You agreed to settle any outstanding amount due. When the bank sold your debt the outstanding amount was settled by the SPV and thus you had no outstanding amount to be paid with said bank.
The outstanding amount and or debt now belongs to the SPV as they bought it. Legally however you have no contract with the SPV so the SPV cannot force you to pay the debt.
The bank should inform you that they will be selling your debt to the SPV and part of that process should include a new contract to be signed between you and the SPV. If not then no agreement exist and thus no means to enforce you to settle the debt.
Above is in very simple terms but that is essentially what it boils down to.
EDIT: What is happening now is that the banks say give you a R500K loan. This is sold for say R550K to an SPV which go on to trade this on the markets. The banks thus already have their money back with profit. They however still milk you for the payments and if you do end up settling the debt they have made R500K + the profit on the sale + your payments + interest.
If you do not pay they take your house, to which they no longer have a legal right thus unlawfully, and sell it.
ALSO, another thing the banks are taken to task with is the way in which loans are made. Legally you can only give somebody something which you own. Thus a bank must have the R500K in actual money in their safe before they can give it to you.
Think of this, if they do not have that money available in actual money then the whole loan agreement is not legally enforceable as they cannot give you what they do not actually own. The way the banks are working now is to give you money which does not exist. The money only exist on paper in their books or on their systems and the loan is thus just a movement of figures.
You need to read up a bit more about this before you will get your head around this but essentially it means that almost every loan done by a bank is not legally enforceable.
PS: Below are links to websites where you can read more about this whole banking story. Note that I do not necessarily agree with any of its content, I just did a quick search for more information.
http://www.ubuntuparty.org.za/2013/06/uk-minister-exposes-banking-fraud.html
http://www.ubuntuparty.org.za/2013/04/how-to-respond-to-lawyers-letters.html
http://www.ubuntuparty.org.za/2013/04/how-to-deal-with-sheriff-of-court.html
http://www.newera.org.za/judgement-opens-a-world-of-trouble-for-sa-banks/