Poor quality aluminium doors and windows

Very poor quality aluminium doors and windows installed in our house by Amina Projects.

We paid most of the quote (as they requested), they eventually installed everything over a period of time after we had to follow up repeatedly. However, no double glazing was done (as per quote), the weather strips fell out almost immediately and two of the windows cannot open and shut properly because they are scew. We have tried to contact them repeatedly so that they can fix the faults and so we can pay the balance...but they are avoiding us completely.