Or you could copy some of the free exercises to be found at sites like English CLUB and email those. If you teach English by telephone, then email is the perfect way to supply your student with texts to be read before the lesson, with material that you will use during the lesson or with exercises to be done after the lesson. It could be related specifically to the group or to any other subject of interest to the group. The way you organise this is up to you. The beauty of email is that the text can be written, transmitted, rewritten, edited, retransmitted etc easily between any number of students working in any location.
Text can be either in the body of the email or attached as a file.
Manipulation and correction is particularly easy. The final product could be published as an email, as a printed document or as a web page. If you have your own home page, or if your school has a web site, it should be a fairly easy matter to publish your students' work. This would give added motivation. There is plenty of scope here to collaborate with students in other schools and other countries.