We have so many nuisance calls in China that, for most people, if they don't know the number, they will not answer. Anyone who knows you will find some other means to contact you. This could be one of the reasons why Wechat (Chinese Whatsap) is the main means of communication here now, even within companies and other business person to person communications.
Nuisance texts have been clamped down on, I know people who used to get 30 everyday. However, telecoms fraud is on the increase.
Cheap international calls has made it possible for people to operate across borders, and avoid local regulations. In the recent years the Chinese government has, with local police assistance, arrested several Chinese gangs overseas and repatriated them for trial in China. I think that in one operation they captured over 100 people operating the fraud.
I think if we adopt Mulder's rule, 'Trust no one', and keep up to date on fraud avoidance advice, then the calls will be no more than a nuisance. But like next doors dog barking at 2 am, there is always going to be some nuisance.