Socially level 3 is not much different to level 4, but economically it is quite different as more businesses will be permitted to be able to trade as long as they are practicing safely. So on the face of it, if your staff are required to support online orders and you can confirm you putting in place the necessarily cleaning and hygiene practices then you will be able to undertake that.
Andy’s right about the difference between Level 3 and 4, however I think your question may relate to the PM’s statement that businesses should prepare for Level 3 prior to Tuesday’s official Level 3 enactment. Between now and next Tuesday Level 4 will still be in place but businesses and schools should prepare for how they will operate from next Tuesday. Details of Level 3 here https://covid19.govt.nz/alert-system/alert-level-3/