Earlier quoted context omitted.
I always answer the call and then joyfully "block/report spam" the number in the Android dialer. Being able to do something to fight back is satisfying enough that I don't ignore the call. I did just switch to T-Mobile and they pass "SCAM LIKELY" as the caller name so I may start declining those.
I have had (in the uk) a few recently - they stopped after the last one after I answered in my best BT Phone Voice "Met Police Duty Officer"
One person insisted on trying to sell a car warranty so I ramped it up a bit. I'm only a little sorry that the person was apologetically crying about "interfering with emergency services" by the end of the call.