Maria,
I am somewhat uneasy to call something like a technoinfrastructure an "actor". For me, an actor is someONE you has the capacity and the will to act. Artefacts can not act by themselves but have inbuilt rules. The question for me then is: who built which rules in the artefact, who was ecluded in using it, which are the "costs"=efforts to use it, who covers for the cost, etc. So, in any case, the artefact is a socially constructing being, not an actor by itself.
Of course, artefacts shape the opportunity and constraints structure of humans (and organisations)  that use them. But this is not the result of an independent will. This is the result of social decisions about the use (or non-use) of specific material characteristics.

Also, I would add to your list economic factors, for instance business models, user tariffs etc. and operational guidelines. The latter is often not considered in sociological discussions of the construction and use of an artefact but it may become the most important part of it as the rules decide how to use the artefact. And, of course, there sometimes is a nice struglle about the rules. Think of the French telecom engineers who conceived the minitel as a centra server model and who were surprised that users linked terminals not to the  server for database retrieval but to link through to communicate with other end terminal users. This was the birthday of the messager services on minitel which had their strongest use when someone invented minitel rose (I guess you have to translate "someone" into: male, below 30 years, single, trained in science or engineering, ...)   . So, the fellow enginners were strongly against this morally incorrect use of a marvel of communication technology. I don't know who made the decision to allow messenger services even when they transported porn, I guess, no prejudice, this must have been people from the finance department. Look into the works of Volker Schneider and his comparison with the British videotext and the German Btx services (together with Graham Thomas and Thierry Vedel).

Did you integrate the videotext services as a precursor in your description ?

Cordialement
Frank