Welcome to Vodafone Community
So I did a phone test and it's saying that I am running on vodaphone 3g and the nearest tower is 3g.
My data is so poor that I am missing calls at my home address which I should be getting 4g. I was on talkmoble and left so I could get 4g, but guess what talk mobile was better.
There has been some posts where a persons sim card hasn't been properly provisioned for 4G.
Customer service on 191 can check this for you.
Is this happening everywhere or just in your home area ?
As a process of elimination can you try your sim card in another phone and another sim card in your phone.
It maybe beneficial to try and select another network in the phones settings and then re choose Vodafone.
Phones nowadays are designed to latch onto the strongest signal which is possibly why its choosing 3G.
I hope this improves for you as I understand the difference in user experience between 3G and 4G is pretty big.
Current Phone > Samsung Note 9 _512Gb > Model: SM-N960 Hybrid-Duos.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.
Phones do not latch onto the strongest signal at all. They follow the network assigned procedure, hence why it's not uncommon to be connected to a weaker signal than is strictly available!