TNT Service declined since Fedex Take Over

For the last few months TNT have been invoicing way in excess of their quotations for shipments. The excuses are laughable - eg The quotation does not include surcharges, even though the quotation actually states at the bottom that it does. Our "Customer Service Agent" (a definite oxy***** here as there is no service) has a Fedex email address. It is very clear that she (her name is Cleopatra Stephens) has no interest in TNT customers. She does not respond to emails and is quite rude. I now have at 3 invoices in dispute - although no one is actually dealing with the issue