What is the ruling on establishing a telephone call center in a non-Muslim country, knowing the high probability of foreign men and women speaking over the phone?

It is permissible to deal with disbelievers in buying, selling, leasing, and similar transactions, even if it is probable that they might use what is permissible for unlawful purposes. Muslims have dealt with disbelievers since the time of the Prophet, peace be upon him. The important thing is that a Muslim should not be certain or highly presume that the buyer or lessee will use what they obtain for something unlawful. If one is certain of that, then it is not permissible to deal with them, whether they are Muslim or disbeliever. Based on this, it is permissible to open a telecommunications center in a non-Muslim country even with the possibility that some might use the service for something religiously prohibited.