A number of mystery shopping companies have telephone shops from time to time. They are not a major focus of the work, so there are not a whole lot of them and the pay is low because many shoppers are interested in saving gas and shopping from home. If those are the only shops that interest you, you will spend a great deal of time just trying to find them. I have picked up 6 for August while looking for other jobs. They pay $3 or $4. There are some that pay more and some that pay less. I only bother with those that the report is simple enough that the call and report can be completed in 15 to 20 minutes or less.
Be very careful about the on line "mystery shopping" opportunities. Many/most of these require you sign up with your real personal data before you "qualify" to get paid. If you don't cancel your "free trial" memberships, you will be paying a lot more than you 'earned'. You also will end up having a "relationship" with many companies who will solicit you at home even if you are on the do not call list. So think carefully before you get into this mess.