Complex sentence: Soon after, Clapton called Robert Stigwood, record executive of RSO, and told him not to release "Tell the Truth" as a single in October, and the reasoning by the band and Stigwood was that the single would hurt future album sales.
Split into simpler sentences: Soon after, Clapton called Robert Stigwood, record executive of RSO, and told him not to release "Tell the Truth" as a single in October. The reasoning by the band and Stigwood was that the single would hurt future album sales.