Probably detect by IMEI, like the early days when they check for 'compatible' device for billing discount before they allowed other phones to use the sim

I think celcom more stable in KL . But webe quite good also , i stay at rawang . Celcom , maxis & umobile no signal in my house . But with webe i can get LTE , every month they give you 10gb hotspot
No , manage your data usage using your phone only