  In this paper we have studied the propagation of a massless scalar field
minimally coupled to a black hole with the source of cloud of strings in $2+1$
$f(R)$gravity theory. In particular we have found analytical results for the
decay rate, reflection coefficient, greybody factors, as well as the black hole
temperature. On the other hand, our quasinormal modes analyses reveals
stability in the propagation of a massless scalar field in the cloud of strings
black hole spacetime. However, under a suitable choose of parameters an
instability is found. Furthermore based on the Bekenstein conjecture on the
quantization of the surface area of the black hole we find the minimal surface
area associated to the black hole horizon which is in agreement with
Bekenstein's proposal.
