QoS in MPLS is similar to doing a translation on PEs.
The objective was to guarantee 640 kbps of Voice traffic as a priority through the SP. Therefor, on the PEs, you need to classify VOIP coming from the CE and also VOIP-Translated coming from the P. Keep in mind that within the MPLS VPN, the labels carry EXP bits (3) so with the SP network you should be dealing with EXP exclusively.
Config:
R3 - PE router
class-map match-all VoIP
match access-group name VoIP
class-map match-all QOS_GROUP_5
match qos-group 5
class-map match-all MPLS_EXP_5
match mpls experimental topmost 5
policy-map TO_P
class MPLS_EXP_5
priority 640
class MPLS_EXP_1
bandwidth 1000
random-detect
policy-map FROM_P
class MPLS_EXP_5
set qos-group 5
class MPLS_EXP_1
set qos-group 1
policy-map TO_CE
class QOS_GROUP_5
priority 640
class QOS_GROUP_1
bandwidth 1000
random-detect
policy-map FROM_CE
class VoIP
set qos-group 5
set mpls experimental imposition 5
class class-default
set qos-group 1
set mpls experimental imposition 1
