i bought a Samsung galaxy Xcover 3 but coverage is worse than my old phone

[AC Question]

I had a Samsung galaxy mini the coverage was okay not as good as my partners J1 but this new phone seems way less powerful when it comes to coverage, is there a way to bump up the coverage?, also I am using my old sim in it, being a phone novice does using an old sim card affect a new phone that is designed for 4G coverage and am I just better off using the new sim.
Thanks