Hi @Paco7222, let me see if I can help out here!
Your post has been translated to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
If you want to change the starting date for the app data usage cycle, find and tap Settings > Network & internet > Data usage > Data warning & limit. In this menu you can both change the starting date for the app data usage cycle as well as set a limit or a warning for the data usage.
If your question regards your phone subscription, I suggest that you get in contact with your service provider.
I hope that helped, please let me know if I have misinterpreted your question in any way!
