Significant delay in voice calling - both on wifi and without.

Same here. WiFi call every Sunday to a landline for 60 minutes. 3 out of 5 calls have to be terminated and redialled after 40 minutes or so owing to the significant delay.

Can't say if the same happens on a cellular call as there's zero signal (of any network) to use. Glad to see it's not just me, disappointed it's not been resolved.

Same here I’m afraid. iPhone 12/Sky Broadband ☹️

This is a smarty problem.
I've done extensive testing with several phones and sims from various providers both piggybacking off 3 and EE; all using wifi calling.
The problem is manifest with smarty sims and wifi calling. Predominately I find it's calling other people on the 3 network who are not using smarty.
Another big problem is the smarty sim keeps wanting to swap back to cellular from wifi even if there is zero bars and a flip to no connection at all. The weakest of signal and it's trying to flip back to the cell from wifi.
Some other providers dont do this.

Calling from other providers back to smarty there isnt an issue. I can call a smarty number from another sim and it will connect. Then hang up and immediately try to call it back and the smarty sim just wont connect.
Be it on the same external IP, or different internet connections, it matters not.

I just discovered this long and old thread, as I have just posted the same problem: voice calling delays, so the other person cannot hear what you say until many seconds, or even minutes later.

Wifi calling is switched off. Android phone.

As this seems to be an old problem, affecting all kinds of phones, which surely they are aware of, I think the only solution will be to go with another provider. Sadly.

Just been experiencing the same issue when I call a certain landline often, this particular landline is supplied By talk talk and after 10-15 mins there sometimes gets a 5-10sec delay between the two of us. As I’m talking to an elderly person with dementia this get very confusing for them, and I find it better to hang up and start again. This doesn’t seem to happen when the landline calls me? 
I mostly call on Wi-Fi calling as the signal here .

Very annoying when trying to keep in touch with someone vulnerable. Maybe Smarty/ Three should look into this issue. 

Wow, thought it was just me, been happening to me since October last year, Samsung Galaxy S23 Ultra and as of yesterday IPhone 16 Pro Max happens for me when ringing all numbers including mobiles regardless of being connected to WiFi or not. I have experienced delays as long as 40 seconds, only way to fix has been to abandon call.

Always assumed it was the Samsung, never thought it could be the network hmmmmm

MSF- There is one landline that I call all the time which is a traditional PSTN line served on copper provided by TalkTalk. (not Digital voice or internet based) When I call this number, the delay happens often but not everytime. Other than that number, it also happens when I call other landline numbers or call centres etc. These of course could be internet lines.

If you also make these type of calls and have never experienced this issue then that's good to know. What device do you use? I've yet to properly try out another device but given this thread exists for diifferent devices - I wasn't very hopefull.

I also have this issue intermittently and normally only when I call fixed lines. It's very random even in the same areas with very good 4G coverage. It's really annoying and I am suprised there aren't more complaints about this as even seems to occur with latest devices. Maybe not many people call fixed lines, but I am having this issue on/off for the last year. This issue does not happen on 3G but with the switch off just around the corner - then my experience is only going to get worse. I thought over time this would be fixed but since it's been a year already, it's not looking likely. 

I'm having this exact issue mid-2024. It's so bad, often the delay even begins at the start of the call. This is extremely frustrating and happens around 50% of the time. Unfortunately SMARTY support is of no use and there is not much about this issue online.  I'm switching to a non 3 run network.  

Im having the same issue - Originally when I was on Three I would call a family member on their landline and after 20-30 minutes a delay in my voice transmission to them would occur.  It would then get so long we would have to abandon the call.  I have since switched to Smarty - who are owned by Three and use Three's network and the same problem happens.  I have made calls over wifi, without wifi, with bluetooth headset and without bluetooth headset yet it still happens. This happens on different phones with the same SIM card in.  It shouldnt be the SIM because as I say I was originally on Three and switched to Smarty and ported my number to a new sim card.