The lists that the companies are given often include inaccuracies--stores that are closed, hours that don't correspond to that particular location, etc. I have saved myself grief by making phone calls in advance because not all companies pay for a closed location. I also have been assigned a Saturday shop at the only store in the chain that is not open on Saturday. If they tell you to call ahead and you don't, if you discover the store is closed when you arrive, don't expect to be paid.
On the other hand, some shops specifically want you to call to check phone courtesy in addition to your on-site visit, so take a look at your report to see what you will need to be reporting about your phone call.