GST on services

Are you registered in GST ???,.

I assume that you are registered in , GST & as the query sounds that whether in FY 2019-20 the turnover not get exceeding the taxable turnover , hence needs pay. GST .
you cannot withdraw Registration in 2019-20 on assumption that your Turnover will not Exceeds 20 lac . for that the previous year turnover is computed.

Hence need to continue & liable to pay GST on supply

Since your turnover in FY 2018-19 is exceeding 20 lakhs, registration is mandatory post crossing 20 Lakhs and GST liability has to be discharged on amount exceeding 20Lakhs (subject to registration date).

In FY 2019-20, you would be continued to be laible for tax as revenue for FY 2018-19 is exceeding 20 lakhs. However you can go for cancellation in FY 2020-21 as turnover fpr FY 2019-20 is less than 20 lakhs.

You will continue to collect and pay tax as you are registered under GST.