After the online loan is paid off, how can people stop sending loan text messages and phone calls?

There is basically no way to do this, just like if you collect some insurance sales, even if you call the police, it will not be solved. Because you have borrowed money from those microfinance companies in the past, and those microfinance companies honestly enjoy the resources, that is to say, your information is likely to be obtained by several microfinance companies.

If you block this message directly, you don't have to answer the phone with a foreign number. If this is a small loan company, just hang up. After a while, the number of phone calls will gradually decrease.