Genuine call?

Hi, I just received a phonecall from the refund department, I was told the engineers found a fault last night and I need to change my router settings/ IP address as I am not getting the proper speed.  

But I am getting around 70mbp download speed as usual, he said if I didn't change it they would need to refund me?  

I had to leave to take my son to school, so I asked them to call back.  

Is this call genuine?  They did not use my name even when I asked them if they had my details in front of them, so I am a bit unsure!!