Most AI answering services charge per minute, typically $0.10 to $0.30 per minute after a small monthly base. That model works for low call volume, but the moment a business hits a busy month, overage bills can double or triple the base cost.
A flat rate unlimited AI receptionist like atAnswer charges one predictable monthly fee no matter how many calls come in. For businesses answering more than roughly 2,000 to 3,000 minutes per month, busy home services, medical offices, real estate teams, restaurants, the flat rate becomes the cheaper option and removes billing surprises entirely.
Rule of thumb: under ~1,500 minutes/month, usage based is cheaper. Above ~2,500 minutes/month, flat rate unlimited wins on both price and predictability.