NSURLConnection/Session. GET request. sending parameters as data, and not part of the URL

I'm only familiar with making GET request from manually constructing a string of parameters. I was told be the by the admin of the API that they are not set up to parse my parameters and that I have to send a JSON array of parameters. In this case, it is a parameter of phone numbers?

I'm familiar with sending data an an POST request via:

NSURLSessionUploadTask *uploadTask = [session uploadTaskWithRequest:request fromData:data    completionHandler:^(NSData *data,NSURLResponse *response,NSError *error

But that doesn't seem like an option to me for GET methods.

Thanks!