Bodyshop issue. Advice required.

[JohnM 25]

I am after some advice regards to an issue I am having.

I had my bodykit fitted about a month ago and was less than happy regards to the colour match. After a messaged discussion regards to the colour match issues I decided that I would have the kit painted a gloss black to match the front skirt. We agreed a price and the work to be completed via a whats app message but today the work has not been fully completed as per that message. The owner is saying he didnt realise that the side skirts were also suppose to have been painted even though it clearly states in the message to which he replied and also a verbal discussion when the car was dropped off regards to the colour required. He is now saying he cant do it at the price agreed and that there will be an additional cost involved, this is ontop of the original fee already paid when they where done in the first place.

What are my options?

Cut my loses and go somewhere else or stick to my guns regards to what has been agreed and previously paint for.

Thanks in advance.