Your case looks like, you are providing services as a pure agent.
First thing, make proper agreements with your clients in future to prove that you provided services as a pure agent to your clients.
Under GST regime, you have to charge GST on all expenses incurred by your to provide services. However in this case since invoices are on name of your clients and client was bound to pay the money, instead you complete their obligations.
It looks like a pure agent service. However, keep proper documents to save yourself from future disputes arising out of any department inquiry.
Since your question is not well formatted, I assume your have concern regarding receipt of entire amount as an advance.
As per provisions one has to pay GST on remuneration received in advance. You are suppose to pay GST on your fee only as remaining amount relates to services you will pay as a pure agent.
Further GST on advance as an requirement was removed. So you need to charge GST based on invoicing.
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