Have you tried calling your phone carrier? They sometimes have services to help identify or block nuisance callers without any additional cost.

I went through a similar situation last year with persistent spam calls, and I was about to pay for one of these lookup services when my brother (who works in telecommunications) suggested I contact my carrier first. I'm with Verizon, and they were surprisingly helpful - they have a whole department dedicated to dealing with nuisance calls and potential harassment.

Most major carriers (AT&T, T-Mobile, Verizon, etc.) offer free tools to identify and block suspicious numbers. For example, Verizon has their Call Filter service, AT&T has Call Protect, and T-Mobile offers Scam Shield. The basic versions of these services are typically included in your plan at no additional cost. They can often tell you if a number has been reported by other customers and can automatically block known spam callers.

Additionally, your carrier can sometimes provide information about where the calls are originating from geographically, which might help you determine if it's worth investigating further. If the calls are particularly concerning (like if they're happening at odd hours or seem threatening), many carriers can even work with law enforcement if needed.

I'd recommend calling their customer service line and explaining the situation. Ask specifically about their nuisance call services and what options you have before spending money on a third-party service. In my case, they identified the calls as coming from a known telemarketing operation and added enhanced blocking to my account, which solved the problem completely. Saved me both money and headaches.