MultiLine apps are built to respect your privacy while delivering the ability to make calls over minutes or VOIP (Data mode).
We must request the Location permission to provide Data calling because your current WIFI network SSID is considered sensitive location information. To provide you calling over the WIFI network SSID you are currently connected to therefore requires enabling Location permission.
For users in the United States, this information may also used in the case you dial 911 and cannot provide your number to emergency services. For location reliability reasons, we recommend making emergency calls over Minutes and only call over Data as a last resort.
If you do not want to provide the Location permission, you'll only be able to use Minutes mode to make calls. See Call Settings: Set Data or Minutes calling modes.