The storm hit speeds of 125 mph and has displaced millions of people. Seventeen people have been reported dead but millions more have been affected by the huge damage caused to homes, livelihoods and crops.
GFA was one of the organisations that called for prayer ahead of the storm, which decreased from a category 5 super typhoon on Friday to a category 4 storm by the time it made landfall on Saturday evening.
"We thank God for answering our prayers to lessen the storm's strength before landfall," said Dr K P Yohannan, GFA founder and president. "Now millions of people need our help to rebuild their lives and to provide hope to those around them."
At least 800,000 homes have been destroyed or badly damaged and around a million people have been forced to seek shelter in relief camps.
GFA field leaders have reported a lack of food, drinking water, electricity and medicine, and say that poor villagers have been worst affected.
The GFA relief teams are distributing clean water, medical supplies, food packs and clothing.
Among those staying in the camps are hundreds of GFA pastors and missionaries, as well as thousands of Christian believers.
"Homes of thousands of Christian believers and hundreds of churches were destroyed," said Yohannan. "These brothers and sisters all had to flee for their lives, but within the relief camps they are still ministering to the suffering and needy."
As Phailin makes its way across northeastern India, GFA fears further damage and especially mudslides in higher ground.
"Please pray for grace and energy for our missionaries and church workers who are ministering day and night to those in need." said Yohannan. "We must bring hope to many who will find comfort in Jesus for the first time through this crisis."