EC25-J Mini PCIe + Rakuten Mobile SIM: ATD Voice Call (CS/VoLTE) Support and Recommended Firmware?

IoT Modules LTE Standard Module
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Questions

  1. With the combination of EC25-J Mini PCIe and a Rakuten Mobile (MNO) SIM, is voice calling via the ATD command (CS Voice and/or VoLTE) technically supported?
    If it is supported, which P/N (part numbers) and firmware revisions are recommended?

  2. On the Quectel Forum there is a post mentioning the new firmware EC25JFAR06M4G_01.007.01.007 as being “all operators” compatible.
    Is this firmware applicable to the modules I have on hand: EC25JFA-512-KJC / EC25JFA-512-DJC / EC25JFA-512-SJC?
    If yes, does updating to this firmware make it possible to use Rakuten Mobile SIM for voice calls via the ATD command?

  3. With the current firmware versions (EC25JFAR06A03M4G / EC25JFAR06A04M4G_DCM / EC25JFAR06A03M4G_SBK),
    the CS/PS registration status remains rejected or incomplete (e.g. +CREG / +CEREG show rejection or not registered), and ATD results in ERROR or NO CARRIER.
    Is it possible to resolve this only by adjusting AT command settings (e.g. AT+QCFG etc.), or is a firmware update to a Rakuten-compatible version mandatory for voice calling support?