Can't make/receive calls but texts and mobile data works and with full bar of signal

[Jimwel]

1. Model Name: Zenfone 9
2. Firmware Version: Android 13 WW_33.0804.2060.142
3. Rooted or not: Not rooted
4. Frequency of Occurrence: Everytime since it started happening

For some reason, my phone suddenly can't make or receive calls. It worked fine for the last 7 months since I bought my phone (late Oct. 2022) but suddenly had this problem lately which started happening around the previous 2 weeks. The weird thing is that I actually have a full bar of signal and I can send/receive text messages just fine and use my mobile data on one of my sims (I use a dual sim and I use one of the sims exclusively for mobile data. However, I'm assuming mobile data works for the other sim as well). I'm from the Philippines so the service providers I use for my dual sim are Globe Prepaid and GOMO (for mobile data).
I've already tested the sims on another working phone, and calls work perfectly so It can't be the sim, but rather the phone itself. I already tried factory resetting the phone and even tried to make calls while volte+wifi call are on/off, to no avail. 

[Julius_Victor]

After you flash it back to stock firmware, you need to go to the firmware update section of your phone and disable automatic updates. Set it to manual. Even though the lastest firmware is available, it won't ask you to download all of the previous updates at once. These needed to be done one by one. Also before downloading, check the version of the firmware to be downloaded and make sure you are not applying "WW_33.0804.2060.142". My phone calls are working at the moment and I have the version prior to this.

P.S. I forgot to mention, this firmware seems to be affecting Globe users. My girlfriend is using Smart SIM and has the latest firmware version, she doesn't have any problems at all. I asked her to try a Globe SIM, and I was not surprised that she had the same issue.

[Jimwel]

I managed to try using a Smart sim just now (borrowed my mom's smart sim) and it does indeed work (outgoing and incoming calls). Could it be a combination of firmware and sim issue?

[Maxazan]

Same here.

Phone was bought in Portugal.

Total disappointment

[dilla- · Accepted solution]

I had the same problem. Got fixed today by making sure 2G is allowed. Just search for "allow 2G" in settings and enable it.

[Jimwel]

This fixed the call issue for my GOMO sim (i mainly use for data), but my Globe sim still doesn't work (for sms/calls).