Welcome to Vodafone Community
I have just bought a galaxy s9 to upgrade from my s7 edge
I never had any problems with my s7 edge I always had 4g signal wherever I went but since using the s9 I get LTE and extremely poor signal everywhere I go
I spoke to an advisor and he assured me a new SIM card would solve this problem but it hasnt done a thing
I still only have lte/3g/2g in options of my settings
Ive heard LTE is basically 3g+ so why since moving to a newer phone have a I been downgraded signal? It seems very strange and also very frustrating
You won't see 4G in the settings, you will see LTE/3G/2G, LTE is the 4G for transferring data over network, select this and you will be able to access the 4G network for your data use. See here: What is LTE?
If you are having problems connecting to the 4G network, follow this link for self help: Network Issues
It is selected in my settings
I've been to reading,Oxford and Birmingham since I got my phone and I barely get good signal. Even when 'lte' is active it's horribly slow
I understand how important it is to have a stable connection, especially now @barnett71. I'd advise completing the below settings:
Settings > Connections > Mobile Networks > Access Point Name > Click the 3 dots in the top right corner > Add > Fill in as below
Name: Vodafone Internet
Authentication type: None
APN type: Default
Also, if you check out the link @AnnS has provided for network checks and fill out the template we can check the network in your area for you.