A welfare call is something done, or arranged, when someone you know needs help. If you can go, or call, you should. If someone is many miles away, and you can't visit in person, or call, it's possible to contact others in their locality and arrange a visit. This includes friends and also emergency/rescue/police. Various types of contact are possible, depending on the desperation of the situation.
Those who provide emergency/rescue public services will understand the term "welfare call", and should usually provide prompt assistance in cases where someone is currently unable to deal with something desperate, or is near the end of their rope. You can call your local 911 (999, whatever), and ask them to connect to emergency service in another location.
After a cry for help, it may be worth considering extra help going forward. The person might not contact anyone the next time.