I am currently using a MagentaMobil Prepaid Max contract. I have started working recently and got a "Vorteilsnummer" from my company. I would like to port my number over to the Business Mobil XL Plus contract that is available in "Telekom Mitarbeiterangebote". 

In the section for selecting my existing number to port in Telekom Mitarbeiterangebote,  "Telekom" is not found in the "Bisheriger Mobilfunk-Anbaiter" selector.

May I know how I can sign up for the Business Mobil XL Plus contract while keeping my current number?