In this post, @nikosT_3cx mentions that "it is highly recommended to use one of our Supported Providers which are Registration based for avoiding any issues if the machine needs to be re-allocated and ip address of the machine changes".
We use a supported provider in Australia who is IP-based. Is there a chance that 3CX could change the public IP of a Hosted by 3CX instance without warning?
as per the following blog post, in order to use 3cx Hosted solution and in case something happens to have no downtime, your SIP Trunks must be Registration based.
We do not say that IP Based Providers will not work, but in case your Public ip address changes, then you will have to contact your provider to change your Public ip address in their records as all your inbound/outbound calls via your Provider will fail.
As you can understand this means downtime for you and this is something we are trying to avoid.
