No, you do not have to pay again. You can request for your membership to be transferred. To transfer your membership, contact the Phi Theta Kappa advisor at the college you are currently attending so the advisor can verify you meet the requirements of that chapter. If so, the advisor will then submit a request to Headquarters to officially transfer your membership.
If you are unsure whom to contact, you can locate the Phi Theta Kappa advisor on your campus by using the Advisor Search.