Empowering the gatekeeper
Do not bypass gatekeepers. Build alliances. You never know with whom you are speaking. For all you know, the "secretary" is the owner.
Source: Sales consultant/author Todd Natenberg
Gatekeepers' jobs are to push you away, but in the same respect it is their job to determine what might be a benefit for the company. Humanize with them. Make a joke. Have fun. Be respectful. Treat them like they are the owner.
And here's an interesting idea – never ask for the person in charge. Assume they are the people in charge. Say you want to meet with them "and whoever else also makes the purchasing decisions." There are two reasons here:
1) Who you think is in charge and who really is could be different people. By letting them say if they are or not, you will get the real answer.
2) At the same time, by respecting them and their importance, you are separating yourself from other sales reps who might trample upon them with disrespect as they try to reach the decision-maker.