Reverse Spoofing? Or 2 People with Same Phone Number?

Recently I bought a new phone (Samsung Galaxy s21) and got a new phone number. I didn't use it for several weeks to make sure I wouldn't be getting unwanted, incoming calls. All good. Then spent hours updating my accounts and contacting family and friends to let them know I was changing my phone number.

I texted one friend and didn't hear back. Repeated several times. Finally called her and found out that she had indeed been getting my texts, responding to my texts, and had tried to call me directly from my incoming texts. But her calls and texts went to a man who texted back to leave him alone, but with unkind language. She emailed me a screenshot of this thread to verify that she was sending texts to "my" number. Another friend also texted me with different results: I received her text on one occasion; but a few weeks later she texted me again and it never came to my phone.

I called Verizon today and was told that it sounds like spoofing. But doesn't spoofing refer to incoming calls and texts? That is, the spoofer does the sending and the victim does the receiving? How is it spoofing if my contacts initiate the call/text and get a live-person-but-not-me? How can someone else have my phone number? Don't phone companies have a block of numbers reserved for their customers only?

I have successfully received calls and texts from some individuals and businesses. But I don't know the extent of the damage, what didn't come through.

Has anyone else experienced this problem? Any suggestions?