post https://api.fastspring.com/accounts/
Update existing customer account information. If you update a customer's email address, FastSpring will apply the change to all active subscriptions in the customer's account. However, past orders and rebills will remain associated with their original email address.
{
"contact":{
"first":"String",
"last":"String",
"email":"String",
"company":"String",
"phone":"String"
},
"language":"en", //ISO valid language code
"country":"US", //ISO valid country code
"lookup":{
"custom":"customKey" //a-zA-Z0-9_- String with length bigger than or equals to 4
}
}