Yes – if you accept credit or debit cards for the purchase of goods or services and you signed up with a merchant agreement with your bank, you are probably required to be compliant as a merchant.
If you perform a service for other businesses and you are involved in their transactional activities or look after a service that affects their PCI compliance, you’re probably required to be compliant as a service provider (or be involved in every customer’s PCI assessment who needs one).