From13.10.2017, service receiver (i.e. Pvt. Ltd. Co.) is not liable to pay GST under RCM in given situation.
Till 12.10.2017, service receiver (i.e. Pvt. Ltd. Co.) is not liable to pay GST under RCM in given situation where the aggregate value of such supplies of goods or service or both received by a registered person from any or all the suppliers, who is or are not registered, exceeds five thousand rupees in a day
Of-course, service provider (i.e. an individual) is liable to get himself registered and pay GST under forward charge in given situation.
So, non-payment of gst by the service provider will not have any legal impact on the service-receiver in given case. This is subject to presumption that contract between two is drafted in such a way, where price is inclusive of all taxes as applicable and / or service provider does not have recourse to seek reimbursement of gst in future from service receiver in any circumstances.
P.S. On good faith basis & for maintaining cordial business relations etc., one can / should always educate concerned vendor about his liabilities under GST, as same will be detected by Dept. sooner or later (specially if you are deducting TDS there-against). But, if vendor still does not want to comply gst law, he will be at very serious risk (for taxes, interest & penalty u/s 74 etc.) and not the service-recipient in given case.
These are ex facie views of mine and the same should not be construed as professional advice / suggestion.