There was a time that a name change on a bill had to be done in person at the offices of Edesur, MetroGas, AySA, and ABL with proof of ownership (escritura) of the property. I have copies of all the forms I received from each of them when I requested a name change.
Updating information with these services is now available online with the option of receiving the bills by email, thereby reducing paper usage. Not only do many bills delivered to my building have previous owners' names, but I'm the only one receiving virtual bills from Edesur and MetroGas.
It seems to me that it is more common for many residents to never bother to have their names on the bills, yet they pay them anyway. Even renters can change Edesur and MetroGas bills to their name. Edesur, MetroGas, and AySA are continually updating their sites for maximizing usage and encouraging users to help the environment by opting out of receiving bills delivered to the mail box rather than the inbox. Eventually, there will be no other option than virtual bills. As of three years ago or more, when property title is transferred to a new owner, the name is changed automatically.for the ABL bill.