ICIC Bank ltd — Unfortunately I chose ICICI

Address:	Mumbai City, Maharashtra, 600088
Website:	www.icicibank.com

I am an account holder for the past 5 years in ICICI bank. I have moved to US and I wanted to update my mobile number. Since I was unable to visit their branch while I was in Chennai, India, I had couriered the required form for updating the phone number to their Mumbai office on Dec 22nd, 2015. The courier was delivered on December 28th, 2015. From January 4th to till date I am communicating in emails as to why the number isn't updated. I am unsure if a mobile number change is a huge process at their end that its taking more than a month to update. This service request was raised by their customer support only. When I tried to check the status it says that there isn't any request at all.
I have not received any phone call till now from their office on this. Even if I try to reach the CC person, they say they aren't the right person to connect.
I was told that the documents that I have sent is lost in their office. Now whose irresponsibility is that?
1st I sent to Mumbai office;then after repeated followups I was told to send the documents to Hyderabad office. When I asked them to co-ordinate and forward the documents to Hyderabad, I am told that they don't have any documents.
I am not getting any responses for any of the request that I raise. Very delayed or nil responses to emails. A process which should not have taken more than 5 days is taking 40+ days with no resolution.