Your question:

I bought a Grandstream phone on your website, I received it and configured it, and everything works fine. However, the phone rings repeatedly at any time of night or day, showing a strange number and every time I answer there is no one.
It is very stressful that the phone rings repeatedly without stopping.
Can you help me solve this problem?

Our answer:

We understand that having the phone ringing repeatedly at any time of day or night can be very stressful. This is a recurring problem in some Grandstream models, but it can be easily solved.

SIP phones and adapters can be easily attacked by hackers or scammers who try to use your SIP line fraudulently.

As a result of several complaints from users, Grandstream has developed protection functions for SIP phones and adapters that allows to reject all calls that do not come from the legitimate proxy. We will tell you here how to block these calls.

For the Grandstream HT502 / 503 and GXW40xx models, you must enable the following options:

- Validate Incoming SIP Message
- Check SIP User ID for incoming INVITE
- Allow Incoming SIP Messages from SIP Proxy Only

For the Grandstream GXP20xx and GXP21xx / 14xx models, you must enable the following option:

- Check SIP User ID for incoming INVITE

For the Grandstream GXV31XX model, you must enable the following option:

- Validate Incoming Messages