Depending on where you live, there are Endesa offices around, often operating as "Inserts" (offices within shops).
See if you can find yours via this link.  If the link doesn't work, let me know which is nearer to you out of Tortosa, Amposta or Santa Barbara and I'll look it up for you.
https://www.gp.endesaonline.com/gp/out_consultarCanales.do;jsessionid=rTVDA0hRlIwMX9B3WcaTOw**.gpNodo1
Like most of the utilities, they aren't terribly accessible.  A suggestion, (if you can get to an office) is to type your problem into Google Translate and then print out the translation (Catalan or Spanish) and take it in with you.  This usually works for me If I'm having problems with the lingo.