Below for your reference the latest revision of IATA rules.

Normally batteries in the package (packed with item or inside item, <100Wh) fall under one of the general categories below:

UN 3481, Lithium ion batteries packed with equipment.
UN 3481, Lithium ion batteries contained in equipment;

If more detailed:
-UN3481 PI 966 Section II IMP: ELI
- or UN3481 PI 967 Section I IMP: RLI

What is Restrictions and Prohibitions:
Prohibitions
Lithium ion batteries
With effect 1 April 2016 all lithium ion cells and batteries shipped by themselves (UN 3480) are forbidden for transport as cargo on passenger aircraft. All packages prepared in accordance with Packing Instruction 965, Section IA, IB and II, must bear a Cargo Aircraft Only label, in addition to existing labels.
Lithium metal batteries
All lithium metal cells and batteries shipped by themselves (UN 3090) are forbidden for transport as cargo on passenger aircraft. All packages prepared in accordance with Packing Instruction 968, Section IA, IB and II, must bear a Cargo Aircraft Only label, in addition to existing labels.
Restrictions
Lithium ion batteries
With effect 1 April 2016 all lithium ion cells and batteries must be shipped at a state of charge not exceeding 30% of their rated design capacity. Cells and/or batteries at a SoC of greater than 30% may only be shipped with the approval of the State of Origin and the State of the Operator under the written conditions established by those authorities.

As you can see as per IATA rules the package is save to send by any way of transportation.

The problem is Shipping Companies , who does not have a clue what they are talking about.

Be safe use this info to fight you right.