Device not falling back to 3G from 4G

[Android Central Question]

Hi,
I have a Lenovo vibe k6 note stock rom on Android 7.0.
Calls are working perfectly in Jio 4G (volte).
Recently I switched to Vodafone 4G (no volte).
When I try to place calls, the device is not falling back to 3G. I am unable to switch the network to 3G or 2G manually also. However 2G works when I change my primary data Sim.
I tried swapping the sim slots, toggling enhanced 4G services, restoring the device software, changing sim cards, replacing my sim card, the same problem persists.
I am using this sim with Lumia 640 XL LTE now. This issue is not present with other phones.
Any help would be appreciated.

 

[mustang7757]

Hi, welcome to Android Forums

I'd like to recommend creating a account so me or other members can assist you, as guest have limitations in replying here and if we need further Information to communicate with you.

I'll provide a link to register, please come back to your post so we can further assist
https://forums.androidcentral.com/showthread.php?t=409154

 

[mustang7757]

Are you having any issues with data , reception?

 

[theflyingrahul]

Hello
I have completed the registration.
I am receiving 4G signal and data works perfectly.
I am not able to place any calls.
On a non-volte network, the network falls back to 3g from 4g when placing calls right?
In my case I am not able to place any calls as the network is not falling back to 3g.
Thus when I try to make a call, the call disconnects immediately.

 

[mustang7757]

Hello
I have completed the registration.
I am receiving 4G signal and data works perfectly.
I am not able to place any calls.
On a non-volte network, the network falls back to 3g from 4g when placing calls right?
In my case I am not able to place any calls as the network is not falling back to 3g.
Thus when I try to make a call, the call disconnects immediately.

Hi, welcome !
Have you talk to your Carrier ? Sounds like APN setting needs to be corrected.

 

[theflyingrahul]

Yeah I have spoken to my carrier.
The APN settings are correct as mobile data works perfectly.
They did perform a network reset and issued a new sim card.
Only then we tested it on a different phone.
Calls are working perfectly on different phones as network falls back to 3G as expected.
Only with this phone, the network is not falling back to 3G from 4G.
Calls are perfect on a different carrier (Jio 4G) which is a VoLTE based network...

 

[mustang7757]

Yeah I have spoken to my carrier.
The APN settings are correct as mobile data works perfectly.
They did perform a network reset and issued a new sim card.
Only then we tested it on a different phone.
Calls are working perfectly on different phones as network falls back to 3G as expected.
Only with this phone, the network is not falling back to 3G from 4G.
Calls are perfect on a different carrier (Jio 4G) which is a VoLTE based network...

Have you tried safe mode , this will disable any 3rd party apps that might cause issues

 

[theflyingrahul]

Yes. Safe mode was the very first thing that I tried.
Also I tried performing a system reset.
Still no luck!

 

[mustang7757]

Yes. Safe mode was the very first thing that I tried.
Also I tried performing a system reset.
Still no luck!

Something definitely wrong with that phone , and you can't make any calls just internet?

 

[theflyingrahul]

Precisely.
Once again, 4G VoLTE calls are working perfectly.
Only when 4G to 3G switching needs to be done, there is some problem.
Internet is perfect in all cases.
Also, when I set my network to GSM only, calls are working.

 

[mustang7757]

Precisely.
Once again, 4G VoLTE calls are working perfectly.
Only when 4G to 3G switching needs to be done, there is some problem.
Internet is perfect in all cases.
Also, when I set my network to GSM only, calls are working.

What's on the list by GSM selection besides it?

 

[mustang7757]

Also this happening in both SIM card slots ?

 

[theflyingrahul]

What's on the list by GSM selection besides it?

I don't get this one.
Can you be a bit more precise?

 

[theflyingrahul]

Also this happening in both SIM card slots ?

Yes on both the slots.

 

[mustang7757]

I don't get this one.
Can you be a bit more precise?

You said you select GSM network ? Is there other options?

 

[theflyingrahul]

Yeah all the options are available. I am able to select between other networks.
I have to specify one thing.
I have 2 sim cards. 1 - Vodafone India (no VoLTE) 2 - Jio 4G (VoLTE)
I have Vodafone as my primary sim (for data). It should be noted that though I see options to set the type of network (GSM/WCDMA/LTE/EvDO), no other options really work than LTE, i.e., I don't receive signal (including GSM) for the primary SIM card.
What I am trying to say is GSM works only for the non-primary sim.
The same is observed when I swap the primary sim.

 

[theflyingrahul]

This is not an operator specific issue as the same is observed with other non-VoLTE operator sim cards also.

 

[theflyingrahul]

I am sure that this issue started only when I OEM unlocked my phone.
I tried to relock my phone after I discovered this problem, no luck!

 

[B. Diddy]

You're talking about Vodafone India, correct? What's the exact model number of the phone?

 

[Rukbat]

On a non-volte network, the network falls back to 3g from 4g when placing calls right?

Not if the carrier is using 2G for voice. Data is still on 4G. (It can't be on 3G.)