At your customer, but i fell off the chair.
Customer : 'I'm not getting the speeds you advertised'
Me : 'Let me take a look... hmmm -85/-90 .. that's not good' .. can you send me a picture of how you mounted the dish?
Customer : 'sends whatsapp with image'
Guess that's what happens when you let customers mount the stuff themselves :) .. don't worry : NOW he KNOWs how to mount it