Data from Statistics showing outgoing calls using mobile and land line shows that mobile has to a large extent replaced landline use and up until 2010 increased usage overall. Since 2010, however, total usage has been in decline
A likely cause is the massive growth of smartphone sales in the same period, offering more methods of communication such as email, WhatsApp, and Facebook.
Source: https://www.statista.com/statistics/461759/landline-vs-mobile-outgoing-call-minutes-germany/