Alibaba etiquette. Can I just stop responding to a seller?

So basically I’ve been working with a manufacturer for the last week trying to work out the design and details of the order. However they started to act strange and are now adding additional fees to my price. I have decided to go with another seller.

Is it acceptable to just stop responding to them? Should I block them? Should I tell them I went with someone else? Just trying to learn Alibaba etiquette and what the best way to handle situations like these is. Thank you!