i had this a lot. and i dont care. i answer that if it is not visible on image, it is lab problem, and link to our print prices. life is too short and many printing services compress jpegs down to 70% before uploading. one common "drug store which sells also car insurances and used DVDs and went recently bankrupt" does that even for printing from DVD.
To avoid at least most issues we however convert to SRGB color profile.
