Our call center charges a low base rate each billing cycle, much like an access fee. The base rate provides 24/7 access to our agents, a provided phone number and an unlimited web portal through which instantaneous account information is available. The low base rate is the only commitment, after that pay only for what is used.
Accounts and services are billed for the time actually used. Because all usage is billed in arrears, there is never a reason to worry about changing rate plan size nor is there ever any concern about paying for unused calls or minutes. There are also never any unexpected "overage" fees.