Chief of Staff is not a formal Cabinet position and does not need to be confirmed. Ditto Chief Strategist and the like. Calling your senators to complain about Bannon is not at all useful, and takes their attention away from things they can actually have an effect on.
Know your Cabinet positions: Vice President; the Secretaries of Agriculture, Commerce, Defense, Education, Energy, Health and Human Services, Homeland Security, Housing and Urban Development, Interior, Labor, State, Transportation, Treasury, and Veterans Affairs; Attorney General. These positions all require Congressional confirmation, and thus can be affected by calling your reps/senators. When Trump wants Giuliani to be AG or Arpaio to run Homeland Security, you can badger your representatives about blocking the nominations.
Ranking with the Cabinet – but appointed at the POTUS’ discretion and not subject to Congressional approval – are Chief of Staff, the heads of the EPA and OMB, ambassadors for the Trade and UN, and directors of the Council of Economic Advisers and Small Business Administration.