I have a voicemail on my cell phone with an unfamiliar voice saying this person has my phone number in their personal directory because they used to know me when I lived in Cape Coral. They announce their name, but it sounds garbled and can't be understood. I could just dial their number back, but I don't want to be calling someone who is just playing a prank.

If you google the number, you'll find a site called tel2name.com.  Here's the tricky bit.  Among the hits you'll get is a thread for tel2name.com and you'll see this:

239-321-1096 - Tereasa Welding, Middle Oak Dr, Fort Myers, Florida

Now if you know Tereasa then all is well but if you want to confirm the listing you'll have to sift through this big list of numbers that are not in numerical order:  See here:

239-321-1096 - Tereasa Welding, Middle Oak Dr, Fort Myers, Florida

Don't know if this helps.  I was up late and thought I'd give it a shot.  Good luck.