Off shore call centers can work, however, they require significant micro management and constant quality control; agent feedback, live monitoring, performance reviews, sales training, etc. It's best to conduct regular onsite visits and/or have a manager onsite that works with you directly.

When searching for a partner, I recommend conducting a pilot phase and asking for references to verify the quality of their work. You also want to verify their technology stack to ensure their solution fits your operations. If not, provide them with your own tech stack (usually an autodialer). You dont want to provide data in a dialer and leads just get burnt due to their systems inability to connect to calls - ie. Scam likely and least cost routing that blocks calls going out. We help call centers across the globe with this challenge.

Anyways, hope this info helped!