Won't fail. But penalty fee in their tnc will be imposed.
I cannot find any clauses of penality fee as long as you pay the first two months fee and no outstanding charges.
https://www.circles.life/sg/assets/pdfs/SG T&Cs.pdf
9.5 If You no longer wish to receive Circles’ Services, You may initiate a termination request. For You to be
eligible to initiate a termination request, You must (unless Circles otherwise agrees):
9.5.1 have been a customer for at least two (2) Billing Cycles;
9.5.2 not be bound by a contractual minimum term under Your Agreement with Circles; and
9.5.3 not have any outstanding Charges with Circles at the time of the termination request.
9.6. Subject to the requirements in Clause 9.5 above, You may raise a termination request through Support
Services at any time (via ‘live chat’ or other available method). Termination requests received before midday (12pm) Singapore Standard Time on the last day of a calendar month shall be processed during that calendar month, with an effective date of termination of the end of the same calendar month. For requests made after midday (12pm) Singapore Standard Time on the last day of a calendar month, the termination process will be initiated in the following calendar month, with an effective date of termination of the end of the following calendar month. The minimum term of Services is two (2) Billing Cycles. Any request of the Customer for termination of Services during the first two Billing Cycles shall be effective at the end of the second (2nd) Billing Cycle.
In the event You or Circles terminates the Services or ‘ports out’ before the end of a calendar month, You will be obligated to pay the applicable Charges for the remainder of the calendar month in which the Services were terminated. Circles reserves the right to not proceed with the termination of the Agreement if You have any outstanding payments at the date of the request for termination. In such an event, a new termination request must be submitted by You once all outstanding payments are paid in full. In the event of a request for termination is made by You after registering for the Services and before the delivery of the SIM card (applicable to mobile services), any applicable registration fees associated with the Services (typically paid at the time of ordering a SIM card on the Circles Website or the Circles App) shall not be refunded to You. You may choose to cancel a termination request anytime before midday (12pm) Singapore Standard Time on the last day of the calendar month in which the request was made.