problem with whatsapp notifications and messages

Hello,

I am using Iphone 5s with iOS 8.3.

Over the period of two months since I have been using Iphone, I have noticed that i irregularly receive whatsapp notifications while I am in Office. Also, at times i do receive the notifications, but when I open the App, there are no messages. Sometimes, it takes hours for the messages to load.

I am using airtel 3G connection. While I know that there are network issues in my office, what I dont understand is that I have been using whatsapp on my previous android phone (Samsung Galaxy s2) for 2 years with same network connection and in same office. I never faced this problem.

Please help me fix this problem.

Thank You