Inaccuarte quote - Poor service!

I am very disappointed with the service from PG glass! A while ago I needed to replace my car's front windscreen and first contacted PG Glass via email for a quote if I should replace via my insurance. I received a quote for R2658.80. It did say that it is based on final verification at the fitment Centre, but since I provided them with the model and make of my car, I assumed it would be in that ball park. Great was my surprise when I was actually charged R7698.10 - 189.53% MORE!! How on earth can I now be charged nearly 3 times what I was quoted??? This is really pathetic and the last time this company will see me!