MikroTik

Hi guys...i want to ask is there any rule to give bandwidth quota for WANs?actually my ISP provides 300 GB bandwidth for Rs.2000.if i exceed this limit i have to pay extra Rs.5000....i m using PCC loadbalancing and want to know is there any method taht when one WAN reaches 270 GB,mikrotik automatically stop that WAN and put the load on other WAN.....
Answers will be appreciated

Few ways. Use script to monitor data or maby make use of traffick monitor in tools to triger reachng the data. Next mark all traffick with connection mark and then routing mark. Create two routes using the routing mark to the diffrint gateways. Enabel route to firs used line and disable second one. Once the event is trigert, run a script that disable first route and anable second route.