Hi F L, thank you for reaching out!
By any chance you have photos of the area you are talking about? Please reach out to our office and we will resolve it should it be a mistake on our end.
But for time being, some parts may appear to be two layers for several reasons:
1) there is a starter strip at the very beginning which goes below your first layer of shingles which may give it an appearance of "two layers"
2) You previously had asphalt ice water shield installed at the first three feet which cannot be removed because it is stuck onto the plywood. This is the tecnology that they used 15-30 years ago. As a result, the first three feet cannot be removed.
We generally take photos of the entire process and picture text it to everyone of our customers for proof of work. You should also have a copy of photos sent to you real time while we were replacing your roof. Regardless of whichever issue, please reach out to us and we will have someone inspect and resolve this issue ASAP. For faster response, please text the 416 number that the technician texted you the photo at. Tyvm!