Sadly not. If you are cancelling in written form, phone number and birth date are sufficient. 

You can send your termination letter to 

Telefónica Germany GmbH & Co. OHG
Kundenbetreuung
90345 Nürnberg
or fax it to: 01805/571766

Thank you for answer… I need to know another thing:

I have to write a letter with my personal info and say that I need to cancel the contract?

Or there is a sample letter to copie? 

Hey @maniamadrid,

please write a personal letter and tell us: your name, your coustomer number / your mobile number and your signature.

Greetings,

Flo