If you paid to have it done, just take it back and tell them it is squealing. If they didn't replace the rotors when they did the pads, then they should have and you may be charged additional for more parts. If they did replace the rotors then they should consider it labour warranty/redo, since new pads and rotors should not squeal.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue