When I bought my new Sim card,from the first day I started getting spam calls and messages. But to stop this stuff thee Gov and the telecom providers have given a method to stop this nonsense. You just need to opt-in into DnD (Do not disturb) for free. You can easily do it directly from dialer or from the provider's website/application. Personally after I opted-in in the past few years I did not get even a single spam/scam calls or messages.
But, when I made Signall (privacy messaging app) as my default messaging app, I started getting hundreds of spam messages. I think making Signal app as default messagaing apps cancels the DnD plan.
Thankfully, my iPhone can ignore the spam callers and they can leave a voicemail (which they very rarely do).