This is their website :

http://repairnchange.com.sg/index.html

impressive right? Well, don't fall for it.  I had called this company to enquire about window repairs. A man by the name of David took the call and was not only rude but told me to look for someone else. First, he was not able to commit to a time - "I will drop by and take a look when I have the time".  Secondly he refuses to give a price estimate which can only mean one thing - to charge you big time when he completes the job. Well, good luck to him with that attitude.  I can't wait for his business to fail big time.

Even HDB licensed windows contractors, the charges for repairs and inspections vary from one another, need to call a lot to compare till you find the one suit to your budget.

I had a terrible experience with Repair and Change New General Contractor. A man by the name of David Ong came to fix my wardrobe door. He spent 15 mins discussing with his staff how to fix it, then proceeded to drive 3 nails into the wood. And he wanted to charge me $350 for the job. When I protested and bargained it down to $200, he started using crudeabusive language. His staff had to apologise on his behalf. I need to caution anyone who's thinking of using this repairman' service. He also runs CCN Aluminium & Renovation.

This co  Repair and Change New General Contractor don't seems to be registered with HDB?   Can they do window repairs?   Maybe you should get a proper licenced co then maybe you have better customer service