Why can't a telecom mobile phone make a phone call, but can answer the phone and receive short messages?

Hello, first of all, thank you for your support to China Telecom. According to your description,

You can answer the phone and receive short messages within 24 hours after the telecom mobile phone is in arrears. After that, you can't use any business. I suggest you pay the phone bill as soon as possible, so as not to delay your normal use.

For details, please consult Anhui Telecom's online business hall.

China Telecom's 4G is officially commercialized! Enjoy the world of 100 megabits. Tianyi 4G shares a better life. For more exciting content, please pay attention to the online business hall of Anhui Telecom. Please pay close attention to the latest preferential activities announced by Anhui Telecom's online business hall and the official Weibo. Please keep asking questions. I wish you a happy life, thank you!