Revco have no right to threaten me

I am absolutely appalled at the threatening SMS messages I persistently get from this company. They are trying to claim I owe SARS money for rental income for the year 2007 - 17 years ago. This is a load of crock. They do not give my tax number, ignore all my correspondence and I have tried to find the numbers and email address they use but absolutely cannot find it anywhere on the Revco website.