Does any of the SIMs have a public IP(I assume you have two, if SIM switch is used)?
What do you mean by "I don't get responsese due to sim switch operation"? Do SMS commands work?
Do you know specific VPN configuration settings you want to change? You could target them using uci commands.
What happened in the first place, why VPN went down?
How do you know IMEI of the device, but not other details?
Could you send it in a private message?