Today most CSPs (Customer Service Providers) will have a policy in place for the duration of postpaid / prepaid calls. This is to help with Revenue Leakage and
potential frauds.
For prepaid IN systems can be configured so that if during the call balance is depleted the
call can still continue even though you are are in the area of “negative balance”.
With Convergence(PrePaid/PostPaid/Hybrid/etc..) granular policy can be applied to “long duration” calls.
In the early days of GSM some “calls” lasted over a day and were force released via manual
intervention.
VBR/ Wallis Dudhnath