Thank you for your question. I will try to assist you in answering it today but please feel free to ask as many follow up questions as you like until you are 100% satisfied.
I am afraid that I do not have good news for you. Unless your contract stated an increase amount and affords you the option of renewal, you can do nothing about the landlord's decision to increase to this amount. This is to say, unless you have already agreed to a an amount for a new lease as I will explain below.
In terms of SA property law there are no limits to the amount by which a landlord can increase the rental, but in practice most leases contain a clause stipulating that the annual increase will be a specified percentage.
If you can rove all conditions for a verbal lease agreement has been met and agreed to, then you can hold the landlord to said agreement but in order to be bale to do that, you will most likely have to resort to legal action which will be expensive and take time to do. This usually has the effect that tenants would rather find alternative accommodation than fight the landlord.
I hope this answered your question.
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