Integration for ProCall Enterprise with DATEV Telephony is done via MetaDirectory Enterprise by connecting MetaDirectory with DATEV Central Master Data and ProCall with DATEV Telephony Basis and then setting up replication.
You will find instructions on how to do this on the DATEV website:
DATEV Telephony Basis: Guide to setting up estos ProCall Enterprise and estos MetaDirectory: http://www.datev.de/dnlexos/mobile/document.aspx?consumer=webApp&document=0904069