Hi Jim, Wow… you’ve had some really bad service! Firstly, I would definitely contest the latter two charges (but maybe that’s just me).
I recently took my costs management a step further by implementing purchase orders for everything I order. Happy to explain how I did this in detail, if its of use to you. In short, I ask for a contract or quote in writing for the amount in full - then I reply with a reference for them to add to my invoice/bill. If the costs don’t match and I haven’t agreed/authorised extra… I request a credit note and politely state that the amount won’t be paid until the adjustment is received.
It took a while to get used to and I’m not ashamed to admit that I’ve stuck a very bright post-it note reminder on my screen to help me with this new habit
The result have been totally worth the this tiny bit of extra effort.
Hope this is of some use!