Occasionally, a client calls me to tell me that the other side’s lawyer reached out directly to them and wants to have a quick direct conversation to discuss the outstanding issues.
In California, Rule 2-100 of the Professional Conduct Rules says that a lawyer may not speak with the opposing party directly (if the opposing party has counsel) without getting the opposing party’s lawyer’s consent.
ABA Rule 4.2 says roughly the same thing.
In litigation or active disputes, this rule is almost always scrupulously observed. But in business deals, where things are less contentious, sometimes people forget.
So, in short, no, if their business folks decide it’s time to bring in their lawyer, you don’t have to take the call without your own lawyer to back you up. The other side’s lawyer can talk to you, but only if you (and your lawyer) consent.