Adherence to stringent measures is necessary to keep the quality intact. Every step in the call center services should be measured against some set parameters. You have to keep the parameters higher than the average at BPO units.
Ideally, an outsourced answering service should have experience in your industry so they can provide you with information on best practices and procedures to improve efficiency, control costs, and meet your overall goals.
You can also choose a quality assurance call center at callcriteria.com/6-roles-of-quality-analysts-for-call-centers-explained/.
Once your account representative understands what you need and how your account should be structured, he or she should provide you with a total cost estimate, not just pricing.
You need to know what an average billing cycle will look like, any setup fees you will be charged for and any subsequent administrative or account update fees that will be applied.
You don't want to deal with anyone who won't be completely forthcoming about all charges. The last step is to ask for references and then actually talk with them.
You need to know that they have been happy with the quality of the call handling their outsourced call center is providing, the accuracy of the information they receive from them, the responsiveness of their vendor and the level of control they feel they have had over their service levels and budget.