All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
First of all, we thank you for your keenness on doing what is lawful and avoiding what is forbidden, but lying is a despised trait and a grave sin.
Allah says (what means): {…and avoid false statement.} [Quran 22:30]
Also, the Prophet warned us against it. Ibn Mas’ood, may Allah be pleased with him, narrated that the Prophet said, "Beware of lying, for lying leads to vice, and vice leads to Hellfire." [Ahmad, Muslim and At-Tirmithi]
Moreover, Abu Bakrah, may Allah be pleased with him, narrated that the Prophet said, "Shall I not inform you about the greatest of the major sins?" They said, "Indeed do so, O Prophet of Allah!" He said, "To associate partners with Allah, and to be undutiful to one’s parents." He was leaning, so he sat up straight [to show the importance of what he was going to say next] and said, "And beware of false speech and false testimony, beware of false speech and false testimony." He kept repeating it until we wished that he would stop. [Al-Bukhaari]
Therefore, it is not permissible for you to lie to the clients and deceive them by saying that you are calling from a country other than the country where you are. The means of lawful earnings are so many for whoever seeks them. Indeed, whoever obeys Allah, He will make the matter easy for him and will provide for him from sources he would never expect.
Allah knows best.