Question: Why can't Bell Canada do simple arithmetic?

My bill consistently has calculation errors for consumption tax charges. The past two months, you have overcharged by three cents, although this amount varies. Conservatively, if you have three million customers and overcharge them each three cents per month, you are illegally profiting by $90,000 every month. I am tired of calling every single month to have it corrected. Please teach your computers how to do arithmetic. Also, if you contact me about this, please do not use it as an opportunity to try to sell me more services. That is very annoying.