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Can I use the head number of a phone number block without a direct dial?

Please never use a head number without a direct dial as an incoming number.

Although a header number may be directly accessible after initial provisioning, this status changes at the latest with the first porting. If you pass on the head number to contacts and customers, you may suffer economic damage.

The header number can be reached at the beginning under certain circumstances, as it is part of a much larger number range with the number carrier. For calls from external networks, a shorter number can therefore already be assigned to the carrier. As soon as the number is ported for the first time, it is published independently in the correct block length in the porting databases. Due to this now formally correct listing, the head number without a direct dial is no longer considered a complete number and cannot be assigned to the number carrier. Such a porting can even take place within providers, so they have no direct influence on the availability of the head number. The specification-compliant usability is unavoidable. Even with a further porting to another provider or carrier, the head number will no longer be reachable.