GST ON ELECTRICITY CONNECTION CHARGED BY POWER SUPPLIER..ON NEWLY OCCUPIED HOUSES

I have received Separate amount of Rs.1548 as GST on Power connection for my new apartment which I have occupied in May 2018.
my query is...
1. whether such Gst amount is correct...if so
2. who has to pay Builder or Owner..bcoz it is the responsibility of the builder to provide power connection as per the agreement
3. if not eligible to charge..then what is the recourse