What should I do if random numbers keep calling me? (pls read details I'm kind of creeped out)?

This is long but bear with me here.

For the past 4 months I've constantly been getting phone calls from random numbers. At first I tried to ignore them and not pick up, but as they called more and more often I picked up. Out of the dozens of times they called me I picked up 5 times. 2 out of those 5 times they hung up immediately.

This is where it gets creepy.

The other 3 times, they asked to speak to "Caitlin", a good friend of mine, going as far as to give her last name. Caitlin hasn't been getting these calls and hasn't given my phone number to anyone, and I haven't given her name to anyone. In fact the only time me and Caitlin can be seen together is when we walk home after school, we haven't spent time together in public at all. One of the three times they asked for Caitlin, she was with me and I handed the phone to her. She said it sounded like it was a busy room and she couldn't understand what the woman was saying because of her accent.

The calls always come from different areas, several from CA but a few scarily close to where I live.

Recently, when I get these calls they hang up before I can answer, and when I call back they're telemarketers.

Though I still get calls I brush them off as telemarketers and don't pick up anymore. But I don't know if what happened a few weeks ago is something I should be taking more seriously?