"She could not look at him, because public telephones were not fitted with television dials"
They never did get round to fitting it out with 'television dials'!
Creative Commons Attribution Share AlikeDilapidated British public telephone box - they never did get round to fitting it out with 'television dials'! - Credit: Tony Atkin, Wikimedia Commons

This is one of the lines in the novel which reminds us that it is set 'in the near future'.

In general in Cold Comfort Farm, Stella Gibbons keep most aspects of social and cultural life close to how they would have been in  the 1930s.

However, at this point she has ventured to speculate on the technology of the future. Her prediction about private telephone users being able to view the person they are speaking to is, of course, very much in keeping with the subsequent development of the videophone.