Mac osx has got much slower than pc?

[denday23]

I really could do with some help on this one as im about to go back to my old PC.(which i dont wanna do)
I have just changed internet providers, i was with Vodafone using a Telfonica cable, was promised upto 6 meg which never happened so changed to a new wireless provider here in Spain that guarantees either 2 or 4 meg depending on the price you pay so i decided on the 2 meg seeing that all i was ever getting before was 0.5 max.
After installation a speedtest showed ping 45 download 2.25 & upload 0.50 so was very happy but very next day i noticed things running very slow again speedtest showed i was back to half a meg called the company out, they connected there laptop to my wifi and sure enough it was showing over 2 meg so we tried it on my wifes laptop the same thing 2 meg my iphone wifi 2meg but on my mac 0.5 so i booted up into windows using bootcamp and got 2.25meg. the company has told me it has to be my mac as they are providing the 2meg to my house. called an pc engineer out to check my mac and even he could not work it out after changing several settings, so any help or advise would be fantastic.
Thanks guys (my first post so fingers crossed)

 

[Satcomer]

Turn off the modem and leave it off for 3 minutes. Then turn off the router you are using. Then after three minutes first turn the modem back on and after about 30 seconds turn the router back on. See if that helps.

Also consider upgrading the Ethernet cables that you have been using for the last few years with some new CAT 6 cable.