Endesa provides you with free customer service phone lines so that you can resolve any doubt you may have.
These numbers are Endesa's only official numbers and they are published in the Contact Us section.
Voluntary Price for Small Consumers (VPSC) Customers - Endesa Energy, XXI 800 76 03 33
Open Market Customers - Endesa Energy: 800 76 09 09
Do not trust web pages that offer 905 telephones or similar numbers and, specifically, calls received from the number 640 013 068.