B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 147
Situational Awareness; Communication Breakdown
ATC Issue All Types
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Procedure; Human Factors
Taxiing toward the threshold of the runway; the Tower Controller cleared us for takeoff. The First Officer repeated the takeoff instruction; and I proceeded to move the aircraft onto the runway. While crossing the runway holding markings; the Tower Controller called us and told us to switch to a different Tower frequency. The First Officer read it back while I was moving the aircraft and tuned the new frequency. I wondered why; of all times; the Controller would choose this exact moment to have us switch frequencies. I now questioned the First Officer whether we were still cleared for takeoff. The First Officer checked in on the new frequency; and received no response. He checked in again; and I held the brakes. At that moment; the Clearance Delivery Controller answered and asked why we were on his frequency; telling us to return to the Tower frequency. So; the First Officer retuned the original Tower frequency. The First Officer explained what happened; and the Tower Controller remarked; 'OK; just stay on my frequency -- my colleagues weren't aware of what I was trying to do.' The First Officer asked if we were still cleared for takeoff; and the Tower Controller verified that we were. To summarize; this was completely unacceptable and distracting as I was moving the aircraft onto the runway and preparing to start the takeoff roll. The Tower needs to understand that we've got a lot going on; and this is no time to start messing around with radios. As it was; I took off; and I realized that I was massively distracted from the task of flying the aircraft. A professional Controller needs to use better judgment.
B737 crew reported being cleared for takeoff while taking the runway at MSP.  They switch frequencies to which a Clearance Delivery Controller answers and sends them back to previous Tower frequency.  First Officer verifies they are still cleared for takeoff.