I have some routers set up wth adsl/vdsl wna 1 and 4g sim lte load balanced to auto wait and load balance by session.( to increase poor bandwidth )
I would like to force the VoIp phone to always use wan 1 and stay off the 4g wan if possible . is there a way to restrict this on a 2862 or 2865

Yes, all you need to do is set up a [Routing] > [Load Balance / Route Policy] rule so that the IP(s) of your VoIP phone uses WAN1 only.
Maybe with failover to "Default WAN" so if WAN1 does go offline, you can still make/receive calls.

hi yes
tried this, but need the phones to fail if the Wan drops out ( it is s complicated issue with our supplier and dynamic IPs) . the phone moved over to the wan 3 even if the failover was not set, which I need to stop .

That's odd. If you need the phones to be offline when WAN1 drops, just having "Failover to" unticked should achieve that. If that's not behaving that way with Failover to left unticked, try updating the firmware.

Beyond that, you can set up a Firewall Filter rule to block the phone's IP from using WAN3 by editing the Direction > Advanced setting in the filter rule.