Have you ever had your own phone call you? (details inside)

What’s happening to me about once or twice every other day is that I get a phone call on my cell phone that appears to be from my own number.
As you know, the phone displays the number that’s calling you, and if it knows the name, it shows that, too. The calls seem to be from me, and it shows my own number.
So, it looks like someone has been able to replace his own number with my number as the source of the call. I don’t answer these calls because there might be a bad guy at the other end, but how do I fix this? Any idea what’s going on?
My phone otherwise works OK.