One common problem with first calls is not getting to the right people, and calls getting no further than the secretaries and receptionists of the companies you’re trying to approach.
As you well know, secretaries and receptionists are the gate-keepers. They don’t make the decision about whether you are awarded a tender, but they may well influence whether you get past the front door in the first place. They control access to important people, and can shape how those people feel about you. How you treat secretaries and receptionists will influence how they talk to the decision-makers about you.
So treat them with respect. Don’t try to manipulate them or bully them. They can smell a salesman a mile off. Be open and honest about who you are and what you want. Speak to them politely, as you would to any potential client. Take no for an answer if necessary, and then politely call back later. Treat them like the full human being that they are! It’s polite, and it’s effective. If you are courteous, well informed and respectful, you’re not likely to be rebuffed very often.