I think all the Nokia phones are supplied through Spark, so it is up to Spark to get this fixed. It is not a Vodafone supported handset. I believe it is a known issue though, so there may be a fix coming in future.
Thank you for getting back to me, I have been a Vodafone customer since the begining aand also a fan of Lumia phones,. I look forward to the fix, (I have since discovewded that itis not just Noklia phones who have the problem, also Xiomi phones. Tony
I have the same problem with a Nokia 6.2 that I set up yesterday. This morning I discovered I couldn't send texts while at home, but when I was out in a marginal coverage area (the phone dropped back to 3G) all of a sudden I could send them. I finally figured out that turning off VoLTE fixed the problem. Hopefully Vodafone will start supporting the VoLTE on Nokia phones soon.