Bad return service

I ordered a white robot vacuum from one day only and when it arrived it was the black model, so I logged a return but I have been waiting now longer than 4 weeks still waiting for the replacement,”. No one can tell me where the vacuum is and they keep contradicting themselves telling me it is with the supplier then in the next email they say the incorrect vacuum is still on the way to the supplier. Nevertheless I ordered the vacuum around 5 weeks ago and still sitting without a vacuum