questrade canada How Questrade is Ripping Off Customers on Margin Interest, Internet

I am a client of questrade since last several months and have been noticing excess interest charged on my margin account. I decided do calculations and have discovered that questrade is ripping me off on margin interest.This may be happening to other clients too. I am in the process of contacting other clients who may be in a similar situation.I am requesting questrade to review this complaint very seriously and investigate this issue that i am bringing up.If questrade does not refund the excess interest charged (starting from the time i was a client), I would be launching a lawsuit on my own account and if warranted a class action lawsuit.

Interest charged on 16 Mar - 843 $ - on debit balance of 230,794
If you check my holdings, there is cash balance of 132,886 Cad (which is at par with usd)
So interest should be charged only on 230,794 - 132,886 = 97,908
Interest @ 4.75% = 387
So questrade has overcharged me by 843 - 387 = 456$ 

Similar pattern of overcharging has occured in past months I want all the excess interest credited back from all past months I will also be writing to the news media , business media about this problem i am facing (probably other clients too) (i wrote to questrade execs - they are refusing to refund the interest, a manager called me saying its their business practice)