And wait the required period of time. It may be unconscionably long, but prepare yourself with coffee and snacks.
Have your form, number, identity documents, or whatever your problem is with you all the time.
Note the number of times you get a ” we value your call but we are busy ” responses. You won’t be able to complain about this or get any satisfaction but you’ll have a bit of a grizzle to throw into the next family dinner.
When the person finally does answer, note their name. Remember this and use it frequently as you speak to them. People like to hear their name.
Speak clearly, but kindly. The phone help person has a rough day of it all the time and they welcome little pools of kindness when they encounter them. They respond by actually helping the caller when this occurs. Nearly all of them can make the changes or registrations that you want to do ( and that the on-line forms made too difficult… ) right while you have them on the phone.
Have your mobile phone handy to receive SMS messages that the agencies send out to confirm you are genuine.
Persist until you are satisfied. Thank them genuinely for their help.
Consider removing this fetter from your life in the future.
Note that if there is a local office that you can get to, use that. Nothing gets something done more surely than face to face contact.