Crazy as a Left Handed Computer

I've been having issue with wifi calling which seems related to the o2 incoming routing to our mobile phones on our own network, two of them. We have an iPhone 12 Pro Max & iPhone 12 that experience the same issue.

The issue is that outgoing calls on wifi calling are absolutely fine but incoming calls are chopping and poor quality, usually breaking up and what seems a routing issues with peering ISPs which we are with Zen Internet.

We have opened up ports (ESP, 4500 UDP and 500 UDP) through a firewall (Opnsense) and it routes to an Asus router internally an Asus XT8 router.

The agents that I’ve talked to seem to not understand anything about the issue which is related to o2 networking and peering arrangements and bandwidth allocation through o2's own network to other ISPs.

Telefónica O2 UK Limited need to pay their fair share of peering costs to other providers!

Had a long discussion with live chat and nothing was achieved, I'm being blocked from accessing the o2 forum and explained about the equality act, freedom of expression and o2 as far as I'm concerned have broken it! The transcript wasn't even emailed to me when requested!

Stated their forum is being monitored by the media, asked for disability accessibility and was advised that I was registered on the forum with disability accessibility. I stated freedom of expression, and they came back about moderation! And I'm still being blocked from accessing the forum. Agent, "sure I'll certainly register you"?

o2 when the software designer and hardware have developed the software down and up to 3.4Khz bandwidth audio over the PSTN they did it wrong it's too complicated! When you receive a signal from the PTSN it does not need to be upsampled to VoIP HD traffic which requires expensive equipment on mass but one can do the process almost completely in software these days, and I suggest you look at buying a company specialising in the area and customise the software, or even better use open source for just low-pass filter.

One doesn't compress the complete audio spectrum one low-pass filters it first to 3.4Khz or you get oversampling of the complete audio spectrum on compression when one should just low-pass filter it and chop of 3.4Khz upwards of the frequency spectrum. Voice over the PSTN does this and you haven't done it that way have you? KISS applies! Don't do anything fancy with the signal from 3.4Khz because there is a time factor in upsampling with chips on specialised upsampling ADC and DAC hardware and delay in doing so, isn't necessary at all. Don't try and do anything at all with the signal it's right already when you go PSTN to VoIP HD and down just do a low-pass filter process only and chop off the top 3.4Khz of the audio spectrum.