Computershare - why are you keeping half my returns on investment?

I just discovered that for the past couple of years I have only been receiving half of my Sanlam dividends from Computershare. I receive all communications (snail as well as electronic) and nowhere can I find a reason for this - I am even registered on their electronic site and all my info there is correct. If you can pay over half why not the full amount? Am I being punished for something? WHY and WHAT? I think it is quite entitled and unacceptable that a company can keep returns on investment from the rightful owner. This borders on ******** behaviour as there is also a loss of interest as well. I have popped off an email - now have to wait for 5 days to hear some silly excuse or new spin on why only half was paid over. I do not have this problem with FNB securities who are over-diligent. I will be finding out how to move my shares asap.