Are restaurans allowed to do this or is it a scam??

Today I had gone to a restaurant in KP (a famous Chinese restaurant), and I noticed a couple of unfair practices. First thing, they had already kept a water bottle on the table, which was okay, but that bottle had the restaurant's name printed on it. We asked if we could get a Bislery or Aquafina bottle, but they refused. How would I know if that water is safe to drink? Second thing, we asked for a coldrink bottle, which had an MRP of 20 rs. printed on it, but they charged us 30 for it. On top it, they applies 5% GST on Coldrink too. Isn't MRP inclusive of all taxes? Charging more than MRP and then applying GST, is this even allowed? They did same thing with Water bottle, It had 30 Rs. MRP printed on it, and applied GST on it too. I know these 10-15 rs. won't make much difference to anyone, and most won't even notice, but these are such unfair practices to make money.