Persistent issues with sim card blocks

Hi everyone,

We are currently facing a critical issue in our network of GSM gateways and SIM banks dedicated to VoIP GSM termination. Our SIM cards are unexpectedly ceasing to make calls, and we’re seeking the community’s expertise to help us troubleshoot and resolve this problem.

Here’s a brief overview of our setup:

  • We operate a network of GSM gateways and SIM banks for VoIP GSM termination.
  • Our system involves converting VoIP calls received via SIP protocol to GSM, connecting the caller and callee seamlessly.
  • The infrastructure runs on a CentOS-based server using the Asterisk system.

The issue at hand:

  • The SIM cards we employ for the GSM termination suddenly stop connecting calls.
  • Despite receiving VoIP calls via SIP without any issues, the problem arises when we convert the call to GSM using our SIM cards.
  • Our assessment suggests that the IP, server, and related infrastructure are not compromised or tampered with.
  • However, we suspect that call-related logs might be utilized to block our SIM cards.

Additional details:

  • We continue to receive VoIP calls from customers seamlessly.
  • The problem arises only when converting calls to GSM using our SIM cards.
  • Switching to a different SIM temporarily resolves the issue, but the problem reoccurs after a while.

We kindly request the community’s assistance in diagnosing and resolving this issue. Any insights, suggestions, or experiences related to similar problems would be greatly appreciated.

Thank you in advance for your time and expertise.

Providing such a service in the UK is, or at last was, illegal; mobile gateways could only be used where one end was within the organisation. Are you sure that what you are dong is allowed in your country? The mobile operator may be detecting a calling pattern that suggests that you are reselling their air interface.

Notwithstanding @david55 's point that this is illegal here in the UK (and likely so in several other jurisdictions) it may be legal in the OP’s country of operation.

@pashakhan -
Do you have any logging available on the GSM gateways?
Do they show that they are receiving the SIP call?
If so, do they show an attempt to place a call over the mobile network?

If the gateway doesn’t show the inbound SIP connection, then you have a problem upstream of the gateway.

If the gateway shows the inbound SIP call but makes no attempt to place a call, then you might reach out to the gateway manufacturer or an appropriate forum for support with the log files.

If the gateway receives the SIP call,and attempts to place a call then you should raise the issue with the network provider for the SIMs concerned.

Even if relaying calls in this fashion is legal in your country of operation, as @david55 says the practice may not be permitted by the network carrier. It might save much time and effort to check with them whether they allow their service to be resold in this manner.

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