do you have oam configured on the pvc ? if not put it on both sides , then you will see the pvc go down , the traffic you see is most likely OAM streaming in from the switch
interface ATM0/0.1 point-to-point
pvc 2/401
oam-pvc manage
you can also do this command look at the F5 counters and the status
sh atm pvc 2/401
ATM4/0.401: VCD: 1, VPI: 2, VCI: 401, Connection
VBR-NRT, PeakRate: 155000, Average Rate: 20000, Burst Cells: 1000
AAL5-LLC/SNAP, etype:0x0, Flags: 0x20, VCmode: 0x0
OAM frequency: 10 second(s), OAM retry frequency: 1 second(s), OAM retry frequency: 1 second(s)
OAM up retry count: 3, OAM down retry count: 5
OAM Loopback status: OAM Received
OAM VC status: Verified
ILMI VC status: Not Managed
VC is managed by OAM.
VC TxRingLimit: 786 particles
VC Rx Limit: 1766 particles
InARP frequency: 15 minutes(s)
Transmit priority 4
InPkts: 62881115, OutPkts: 62629010, InBytes: 3433130546, OutBytes: 866896572
InPRoc: 106466, OutPRoc: 106465
InFast: 62774649, OutFast: 62522545, InAS: 0, OutAS: 0
InPktDrops: 0, OutPktDrops: 0/0/0 (holdq/outputq/total)
InByteDrops: 0, OutByteDrops: 0
CrcErrors: 0, SarTimeOuts: 0, OverSizedSDUs: 0, LengthViolation: 0, CPIErrors: 0
Out CLP=1 Pkts: 0
OAM cells received: 75584
F5 InEndloop: 75584, F5 InSegloop: 0, F5 InAIS: 0, F5 InRDI: 0
F4 InEndloop: 0, F4 InSegloop: 0, F4 InAIS: 0, F4 InRDI: 0
OAM cells sent: 75590
F5 OutEndloop: 75590, F5 OutSegloop: 0, F5 OutRDI: 0
F4 OutEndloop: 0, F4 OutSegloop: 0, F4 OutRDI: 0
OAM cell drops: 0
Status: UP