Airtel phone
Shifting charges added in my bill

Hi My name is Anil My airtel land line number is 01204568751

At the time of shifting of my land line number they told me they will not charge me anything

But in my recent bill they have added shifting charges of 300 rs

Also they shifted after 1 month instead of two or three days

Please help me to know what action i should take in this matter

Thanks

Anil