Hi,
Each phone service provider has their own method to alter the time that a phone will ring on a call before either diverting to voicemail (if you have it set up) or disconnecting the call. Usually it ranges from 5 up to 30 seconds in 5 second steps but again it depends on what options your phone service provider has provided
Altering the ring time is usually done by dialing a code number from your phone.
Go to your service provider’s website and search for “''change number of rings''” (or similar) to find the code. Alternatively search online for ''change number of rings (insert mobile phone service provider’s name)''
Here’s a [https://lifehacker.com/change-how-long-your-phone-rings-before-sending-calls-t-5878635?IR=T|link] that may be of some help if you live in the USA or this [https://www.lifehacker.com.au/2012/01/make-your-mobile-phone-ring-for-longer/|link] if you live in Australia