Just simply renaming the image will solve this problem. Because you are uploading image with same exact name the path for this image is same, so when it is cached and sent trough CDS, the path(link) because of the name stays the same, so just renaming it will solve the problem.
On the other hand if you have Jetpack installed, you can easily find photon in Jetpack settings menu. So there you have list of all features turned on. There you can find photon and turn it off.
I hope this helps.