It could be "caller ID spoofing." There are applications available now that can mask your caller ID and make it look like any number you want. Without these calls showing in your call log, more than likely it's not your phone making these calls. Your call log or calls billed to a statement could also be used to verify this.
Sprint S.M.A.R.T Agents Sprint S.M.A.R.T Agent are here to help Monday through Friday 6:00 AM CT - 6:00 PM CT. If you need to speak to an agent outside of these hours, please visit Sprint Chat