why ret do not return??

I have been work on the UPSD3354DV mcu, my application is large than 64k, so I use the
bank1 and bank2 as code area. now I want to use other bank(like bank3) as data area, but
when select bank3 before erase it. It do not ret from the select function.
here is my code segment
//pg_vm.A51
PUBLIC PG_VM_CALL,PG_VM_RET
;
PG XDATA 7FE0H
VM XDATA 7FE2H
PG_BFR EQU 40H
VM_BFR EQU 41H
PG_OLD EQU 42H
VM_OLD EQU 43H
;
asm_PG_VM SEGMENT CODE
RSEG asm_PG_VM
USING 1
;===============================================;
PG_VM_CALL:
PUSH ACC
PUSH DPH
PUSH DPL
MOV DPTR,#PG
MOVX A,@DPTR
MOV PG_OLD,A
MOV DPTR,#VM
MOVX A,@DPTR
MOV VM_OLD,A
MOV DPTR,#VM
MOV A,VM_BFR
MOVX @DPTR,A
MOV DPTR,#PG
MOV A,PG_BFR
MOVX @DPTR,A
POP DPL
POP DPH
POP ACC
RET
;===============================================;
PG_VM_RET:
PUSH ACC
PUSH DPH
PUSH DPL
MOV DPTR,#VM
MOV A,VM_OLD
MOVX @DPTR,A
MOV VM_BFR,A
MOV DPTR,#PG
MOV A,PG_OLD
MOVX @DPTR,A
MOV PG_BFR,A
POP DPL
POP DPH
POP ACC
RET
;===============================================;
;
END

//call pg_vm_call to select bank
unsigned char idata *pPGVM = 0x40;

pPGVM = 0x40;
*pPGVM = 0x07;
pPGVM = 0x41;
*pPGVM = 0x1F;
pg_vm_call();
erase_bank(0x8000);
pg_vm_ret();

I trace the code. It do not ret from pg_vm_call, just step into the pg_vm_ret();

why it do not ret from pg_vm_call()??