What kind of work can I only read text messages during working hours, but I can't send text messages?

In the general service industry, customers are not allowed to send short messages directly, which is a disrespect to customers. There are also some work units that stipulate that you are not allowed to call and send text messages during work hours, because this will affect work efficiency. The workload of this regulation is very heavy, so I won't explain it one by one.