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Just because there are no complaints doesn't necessarily mean the customers are satisfied.
Literal
Complaints [subject-が] not-exist [just-because-からといって] customers [subject-が] satisfied-being [not-necessarily-とは限らない] [explanatory-のです].
A business wisdom sentence using two important grammar patterns. ~からといって ('just because') sets up the false assumption. ~とは限らない ('it's not necessarily the case that') negates the assumption without fully denying it — a nuanced hedge. クレーム (from English 'claim') is used in Japanese business to mean 'complaint.' お客さま ('customer,' with the respectful さま) is standard business language. The combination of these two patterns makes this a textbook example of logical nuance in Japanese.