I have ever heard of FTTC at 2.5 Mbps, so assuming we mean 2.5MBps ie bytes, so 20Mbps ie bits per second, perhaps ? Lower case b means bits, upper case B means bytes.
Or perhaps 2.5 Mbps ie bits per second is the speed of the wireless lan not the FTTC.
Anyway, precious little chance of getting some services to work at such a low speed, since they require 3Mbps (ie bits per second).
Would need to run a network cable, and if the device does not accept an ethernet connection into it, then place a wireless access point suitably near the device in question, on the end of the network cable.
A wireless LAN speed of 2.5 Mbps is the rock bottom speed that you might get when the station is desperate, with extremely attenuated signal, either by walls, foil-backed plaster or great distance. Interference from neighbours could well be having a disastrous effect, so switching channels, preferably switching to one of the many free 5GHz frequencies would cure that. However, if attenuation due to walls has not be cured first, switching from 2.4GHz to 5GHz will make things worse, because 5GHz has worse penetration of barriers according to some.
A really good wireless access point is your friend here.