Internet while on a call

Hi all, not sure if anyone can help? I've been with Lebara a few weeks, and I'm struggling with the network.
The biggest issue is I don't get any Internet whatsoever whilst on a call, absolutely nothing, no email, WhatsApp messages etcit completely cuts off on starting a call, leading to a barrage of messages on ending a call.
I've tried customer support, who are useless. And tried to speak to technical support, who promise a call back that never arrives.
My phone settings are all fine, any ideas before I ask for a PAC code and leave?

Its because there is no 3g network anymore as Vodafone shut it down as all networks will.
Voice calls are made on 2g or 3g only
So when you make call it drops onto 2g.
This will happen with all networks when 3g shut off.
Only way to stop this is enable VoiceLTE(VOLTE) on your phone. This makes calls over data network instead of old network.

Hi, thanks for your reply, however, I do have volte activated.
I've never had this with any other net

Were you aith o2 as it hasnt shut down 3g yet. Vodafone's / EE / Three all gone only o2 has there's left.
Have you got correct lebara access point setup

I've been with EE 20 years, never had any problems with this before, I've used lebara configuration texts sent by them to install apn settings.

Sounds like volte is not working on your phone

Hi mate, thanks for trying to help, I got more help from you than anyone at Lebara, I appreciate it.
My volte settings, and phone are working perfectly, I've given up with lebara, got another esim installed last night, works a treat on 5g whilst on a call.
Obviously an issue with the network, it's not good enough for my needs, number ports over Monday, Me and lebara are done.
The Indian call centres are useless.
I couldn't even speak to technical support.
Thanks for your help.
Over and out Lebara.