Well Apple are sending me a replacement phone so although they say it will be new i am thinking it will be a refurbished unit.
I will update you on that one as i can tell by the codes in "model number" when you go into settings - about as it should start with a letter M if its new from Apple, See the codes below if you aren't familiar with them.
The first letter of the model will tell you if the iPhone is new, a replacement,
refurbished, or personalized
M – it means your iPhone is a new device, which
was purchased from Apple Store Online or
Apple Retail Store.
F – it means your iPhone is a refurbished
device.
N – it means your iPhone is a
replacement device, which means that it was replaced by Apple or Apple
Authorized Service Center due to a problem. Replacement iPhones are usually
refurbished
P – it means your iPhone is a personalized
device, which means that the device has a personalized engraving.
Whether or not the replacement phone will cure my issues with calls remains to be seen so will update this next week once received
Personally i believe the iPhone 12 models have issues with the aerial antennas as thats the only thing that gives you signal and calls although Apple deny any issues