In a place with a lot of people, the mobile phone signal is normal, but I can’t make calls. Why do I send text messages?

It is mainly caused by network congestion. The capacity of the base stations around your school is so large. Thousands of people occupy the resources of the surrounding base stations at the same time. There will definitely be congestion, not interference. If you do this In other words, when there are more people, signals will interfere with each other. So if there are so many people using mobile phones on the street, there will be interference. So why are communication operators so aggressively promoting their networks?