Is the phone in the arm rest a mid 2000s flip phone in a cradle? That phone is a paperweight now. Better than my 98, it had the factory analog phone when I bought it. That phone is a real antique, about as useful as a tube TV with rabbit ears.

If so that cradle can be removed and a Bluetooth adapter installed in its place.

Have a look at Home

You can go on eBay to find these. However know that there are 2 versions. The older one is cheaper but it is flaky. The newer one is better. When we bought the ML we got the dealer to include one with the deal.

My wife's 08 ML 320 CDI has the same system as your 05 E320 CDI. She has an iPhone 5C and it connects and works fine. However in order to trigger Siri she has to hold in the home button on the phone itself. But if the phone rings she can answer it from the steering wheel.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech