29 CFR 779.350: The section 13(a)(4) exemption does not apply to service establishments.

The section 13(a)(4) exemption applies to retail establishments engaged in the selling of goods. It does not apply to service establishments. If the establishment is a service establishment, it must qualify under section 13(a)(2) in order to be exempt. A retail establishment selling goods, however, also may perform services incidental or necessary to the sale of such goods, such as a delivery service by a bakery store or installation of antennas by a radio dealer for his customers, without affecting the character of the establishment as a retail establishment qualified for exemption under section 13(a)(4).