Random people are getting calls from my number that aren’t me

I just switched over from a cheaper cricket brand phone to an iPhone 6, I kept my phone number and simply transferred everything over from my old phone. Today and yesterday I had people either texting or calling me to ask who I was and why I was calling them. The thing is, I never called them, but both had proof of a missed call from my number. What’s going on and how do I fix this?