Cisco WAN :: Reconnection 819 Router After Connection Failure?

I have a Cisco 819 WAN Router (C819 Secure M2M GW (non-US) 3.7G HSPA+ R7 w/SMS/GPS).Software: Cisco IOS Software, C800 Software (C800-UNIVERSALK9-M), Version 15.2(2)T, RELEASE SOFTWARE (fc1)
 
For dialing in at my Provider (T-mobile Germany), I use the following chat-script:
 
chat-script gsm "" ATZ "" AT+CGDCONT=1 "OK" "AT!SCACT=1,1" TIMEOUT 60 "OK" "ATD*99#" "CONNECT"
 
Dial-In is successful after Reboot.Now, i want to simulate a conenction fault, e.g. termination by mobile provider.So I used the command "clear int cellular 0".After that, The router can't dial in again.
 
Debug shows:
 
Dec  7 11:04:03: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to down
Dec  7 11:04:14: CHAT3: Attempting async line dialer script
Dec  7 11:04:14: CHAT3: Dialing using Modem script: gsm & System script: none
Dec  7 11:04:14: CHAT3: process started
Dec  7 11:04:14: CHAT3: Asserting DTR

[code]...
 
Is the "clear interface cellular 0" the wrong way to test this, or why can't the Router reconnect?The only solution is a reboot, but that is not the best option. The router should automatically redial.