Make resolve.conf persistent

 Edit file /etc/dhcp/dhclient.conf

supersede domain-name "ims.mnc001.mcc001.3gppnetwork.org";
prepend domain-name-servers 192.168.0.189, 192.168.0.1;

edit file /etc/systemd/resolved.conf

DNS=192.168.0.189
FallbackDNS=192.168.0.1
Domains=ims.mnc001.mcc001.3gppnetwork.org

restart resolved

systemctl restart systemd-resolved

check resolved status

resolvectl status
Global
           Protocols: +LLMNR +mDNS -DNSOverTLS DNSSEC=no/unsupported
    resolv.conf mode: foreign
         DNS Servers: 192.168.0.189
Fallback DNS Servers: 192.168.0.1
          DNS Domain: ims.mnc001.mcc001.3gppnetwork.org

Link 2 (enp0s3)
Current Scopes: LLMNR/IPv4 LLMNR/IPv6
     Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

try restarting the server to confirm if the entries in resolved.conf are persistent or not.

after restart check

$ cat /etc/resolv.conf
domain ims.mnc001.mcc001.3gppnetwork.org
search ims.mnc001.mcc001.3gppnetwork.org
nameserver 192.168.0.189
nameserver 192.168.0.1
nameserver 192.168.0.1

Enjoy ;)