Even a simple change of address is difficult. Eight months after trying to change her address we received a check for one of her minimum distributions to her old address. I speak to the rep at least once a quarter and every time he has to ask me for phone number again. It's been frustrating.
Their entire schtick is to courteously and politely promise whatever you want to hear, get you off the phone, and then just go on to the next call with no intention whatsoever of doing what they just promised to do.
They let you wait days, weeks, or months--whatever--to come to your own realization that you just got blown off.
I would recommend that when you ask for an address change again, that you keep them on the phone for as long as you need to in order to get them to agree to send a confirmation letter to the address they said they just changed to.
When they resist (they will come up with some excuse), just escalate. Keep telling them that it took you 8 months to realize they blew you off the last time, and that you're not prepared to wait another year for evidence that they haven't yet got their act together. Eventually, they will ask,
"is there anything else I can help you with?" Explain that they haven't helped you with anything yet. Don't be bashful. Then just start from the top again, and continue to grill them.
When you get someone who promises to send you a confirmation letter you will then have a time-frame for when you have to call them back and do the same thing again, when the confirmation letter doesn't arrive. Be prepared to keep cycling through this same process multiple times. Keep them on the phone longer and longer. Look up the time-zone they are in, and call close to quitting time. Take names, record dates, and take minutes of the conversation. This will give you material to use to keep them on the phone longer next time. Open-ended questions are a great way to keep them on the line longer. When they give you some vague answer, drill down with another open-ended question regarding that answer. Rinse and repeat.
It's sad, but true. These guys have a very well-rehearsed process to just get you off the phone as quickly as possible, and move on to the next call. It's not a broken process. This is their intended process. If you can't cash the check, because you never got it, then the money stays on their balance sheet for another reporting quarter.
The sooner you realize that they will force you to become an S.O.B. eventually, the more quickly you will be able to get this resolved.