Issues with glass after it was replaced by contractor

So a contractor replaced several windows in the winter garden (in November), before we bought the house (got the keys end of January) and after moving in in February we noticed there seems to be water between the two glass panes of one of the windows.

I called the contractor already on 21st of February and told him, he told me to check whether the water is from the inside or the outside, because he couldn’t imagine it was between the glass.

Checked that on several days and send him a mail on 28th with images and a description of the damage saying the water/humidity is definitely between the glass.

On March 10th I wrote him again, because I hadn’t heard anything from him.

On march 14th I called him, because he didn’t reply at all. He was kind of annoyed and said he doesn’t really do mails and there was no phone number in my mails (he did call me before though regarding something else). He claimed he didn’t really get what the issue was from my mails and decided to do nothing.

I send him another mail on March 14th explaining the issue again and adding more pictures and my phone number, so he can’t use that as an excuse for not getting back at me.

I highly doubt he will get in touch himself or even come and take a look at the damage.

What would be my next steps after waiting like a week or two?

I do have a copy of the bill the previous owner received from the contracted for the exchange and her mail saying that this specific window has been exchanged by him.