Problem with the phone call [F(x)tec Pro1 X Dual-SIM - 382114]

I have a problem with the phone call function. Please let me know how to fix it.

- Setup steps

1) I inserted the SIM into the phone 2) APN was automatically set carrier is Ymobile SoftBank)) 3) I set the preferred network to LTE/WCDMA

- No problems with communication functions such as e-mail.

- When I make a phone call, the sound from other phones to the Pro1X can be heard normally, but the sound from the Pro1X to the other phone is intermittent, making it difficult to talk.

- I can make calls with other calling apps such as LINE) without any problems.

Please let me know if there are any setting items that I need to check or any additional setting items.

Please inform customer service

I see. Thank you.