Just keep trying, that is the right way to do it, and if everything is ok with your ULF, it should work.
Does the phone work if you put it into the armrest holder?

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X5 4,4i-06 Current
330Ci Cab-03 2007-2008
MB E55 AMG-03 2006-2007
Z3 2,8 Roadster-98 2006-2007
X3 2,0d-05 2005-2006
320d-99 1999-2005