Do you have to have a telephone service?

That depends on how you define need. For today's world to run properly in the delivery of services goods the organization of care and medical facility's and virtually every aspect of everyday life a good system of communication is required. If we were to cut the telephone system today people would die as a result within 10 minutes, If we are not concerned about this then you can say we do not need telephones. After all we can do without most things but we chose not to.