>What if instead of hiring someone, I pay some other company to do it? Who am I exploiting then?
You are not directly exploiting anybody. You are buying from the company within the market, so on average you will pay the value of what you purchase. Within the company, the employees are paid less than the value of their labor, so the company exploits them. You could say maybe you are supporting that exploitation, but since almost all business works that way it's not like you have an alternative (although if you reasonably could buy from a worker co-op it's different). In reality, it's more likely that the company is exploiting you
the consumer (even if you are another company) because it's more likely that the company is a monopoly charging inflated prices than if you were taking advantage of them (since they would refuse to sell if it wasn't profitable to them). A lot of companies (especially ones with very high fixed capital to variable capital ratios) have been shifting their profits from wage-based exploitation to consumer-end exploitation through price increases (ISPs for example) and rent-seeking (everybody trying to sell you a Premium Subscription for example).