hiya @nabeel1980 i am assuming by WIFI you actually mean your mobile data coonnection having a new sim card shouldnt effect your wifi connection, however this can have an adverse effect on your phone ability to connect to the internet using its data connection please follow the guide i have created below
Please start by checking your APN settings are correct.
By following the link below you can enter your settings in manually the guide includes settings for the most popular devices on the market e.g. Android(HTC , Samsung, Xperia etc) iOS(iPhone, iPad) etc.
guide that allows you to select the network manually. turning of your phone periodically can also help
If you need anything more we are standing by to reply hopr this helps