Incorrect amount

At Old mutual I had a save and invest where R400 was deducted from my payslip every month however each time I checked the Old mutual app it shows R235 instead of R400 I started saving in March , so every month it added R235 on top of another R235 so it was happening every month , I've been calling the company but no one can explain why this is happening. I've requested for a statement from the backoffice no one replies .... I want to know what's going on and I want my money back