What settings to change to avoid signal BUSY?

SIP phone when the status of the feast begins to exceed >50ms, then dials not poluchetsja, the answer is a busy signal.
Tell me what the settings on asterisk or on the telephone Grandstream need to change to avoid this?
Everyone is busy/congested at this time (1:1/0/0)
 -- Executing [s@macro-dial-one:38] ExecIf("IAX2/500-to-200-9501", "0?Set(DIALSTATUS=)") in new stack
 -- Executing [s@macro-dial-one:39] GosubIf("IAX2/500-to-200-9501", "0?s-BUSY,1") in new stack
 -- Executing [s@macro-dial-one:40] MacroExit("IAX2/500-to-200-9501", "") in new stack
 -- Executing [s@macro-exten-vm:10] GotoIf("IAX2/500-to-200-9501", "0?exit") in new stack
 -- Executing [s@macro-exten-vm:11] Set("IAX2/500-to-200-9501", "SV_DIALSTATUS=BUSY") in new stack
 -- Executing [s@macro-exten-vm:12] GosubIf("IAX2/500-to-200-9501", "0?docfu,1") in new stack
 -- Executing [s@macro-exten-vm:13] GosubIf("IAX2/500-to-200-9501", "0?docfb,1") in new stack
 -- Executing [s@macro-exten-vm:14] Set("IAX2/500-to-200-9501", "DIALSTATUS=BUSY") in new stack
 -- Executing [s@macro-exten-vm:15] NoOp("IAX2/500-to-200-9501", "Voicemail is 'novm'") in new stack
 -- Executing [s@macro-exten-vm:16] GotoIf("IAX2/500-to-200-9501", "1?s-BUSY,1") in new stack
 -- Goto (macro-exten-vm,s-BUSY,1)
 -- Executing [s-BUSY@macro-exten-vm:1] NoOp("IAX2/500-to-200-9501", "Extension is reporting BUSY and not passing to Voicemail") in new stack
 -- Executing [s-BUSY@macro-exten-vm:2] GotoIf("IAX2/500-to-200-9501", "0?exit,1") in new stack
 -- Executing [s-BUSY@macro-exten-vm:3] PlayTones("IAX2/500-to-200-9501", "busy") in new stack
 -- Executing [s-BUSY@macro-exten-vm:4] Busy("IAX2/500-to-200-9501", "20") in new stack
 == Spawn extension (macro-exten-vm, s-BUSY, 4) exited non-zero on 'IAX2/500-to-200-9501' in macro 'exten-vm'
 == Spawn extension (from-trunk, 506, 1) exited non-zero on 'IAX2/500-to-200-9501'
August 23rd 19 at 10:38
1 answer
August 23rd 19 at 10:40
qualify=2000 ?

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