Place of supply for onsite services by technical staff

Telecommunication services includes following services to any person –

Data transfer

Broadcasting

Cable

Direct to home television services (DTH)

If the leased circuit is installed in more than one State then all the states will be considered as place of supplies in proportion to the value of services. The states will share GST in proportion to the value of services. At present all the cases of telecommunication services, the supply is intrastate. This is because service providers will now need to register in every state where they supply taxable services.

The employer company was charging IGST to its clients, now they will have get registered in each state of work, get separate GST registration and charge CGST & SGST??

Definitely if the service provider provides services in different states, it requires registration

As per Section 12(11) read with sub clause (d) if the supplier have the full address of recepient , the POS will be Recepient place , else POS will be supplier place .

No need to obtain Registration in Every State :
Section 22 Of The ACT Reads As 'Every Supplier Shall Be Liable To Be Registered Under This Act In The State Or Union Territory, Other Than Special Category States, From Where He Makes A Taxable Supply Of Goods Or Services Or Both, If His Aggregate Turnover In A Financial Year Exceeds Twenty Lakh Rupees, Provided That Where Such Person Makes Taxable Supplies Of Goods Or Services Or Both From Any Of The Special Category States, He Shall Be Liable To Be Registered If His Aggregate Turnover In A Financial Year Exceeds Ten Lakh Rupees.'

"PLEASE NOTE FROM WHERE....MEANS WHERE HE IS REGISTERED"

You can supply your services by charging IGST if its supplied out of state.