Buyer not getting name changed in authorities after buying property

Hello All, I belong to Ahmedabad (Gujarat). I have recently sell by flat in Ahmedabad. My concern is that the buyer is not changing the name in: 1. Torrent Power Electricity board (company that provides electricity in Ahmedabad) 2. Adani PNG Gas (company that company PNG gas supply). 3. Ahmedabad Municipal Corporation property tax. Because of above, the bills of these are still coming in my name, as the buyer has not done the process of name change. I have requested him few times and he is saying yes he will do it but not actually doing it. My concern is that as these bills are coming in my name still, am I responsible to pay it although the property has been sold or what. I am confused and getting what to do. At worst I am thinking that I will not pay it and let the companies disconnect services, then ultimately the buyer will have to do process. Can someone please guide. I needed I can provide more information or details.