Send sms using smsbox API in ASP.Net

i have link of api , how to call it

http://smsbox.in/SecureApi.aspx?usr=BBSP&key=2AE05CBC-557D-45FE-BF59-CB4E4A71B734&smstype=TextSMS&to=8888888888&msg=Hi&rout=Transactional&from=BBSP

and 8888888888 is number on which we are going to send message Hi.

i also want to replace phone number and meaage with variable, that contains number and sms content.