Signal worse after phone upgrade

[Redhotrods22]

I've recently upgraded my o2 supplied phone from a galaxy S11 to a S21 FE. 

With the S11 I had excellent 4g coverage throughout my daily business routines. However, changing phones and sim card for the upgrade has seen my signal deplete significantly at home, work and in general everywhere else. My wife's phone is with O2 and had considerable signal in comparison to mine in the same areas. 

It's got to a point where I'm embarrassed to make business calls with this phone, as I never get to complete a call without repeating wither myself or the client. 

Surely either the phone or sim card is not fit for purpose?

[Cleoriff · Accepted solution]

@Redhotrods22 

Check these guides Guide: How can I sort out my network issues? Guide: Do you have poor coverage / signal Indoors? This may help Explain / resolve it 

Just to add, if you think the phone is faulty, you can return it within 30 days. https://www.o2.co.uk/help/device-and-sim-support/returns-and-repairs