As this question is about a different AXL request, moved to a separate discussion thread...
Carlos, per the AXL schema, your request can have either <addMembers> or <members> elements, but not both. If you intention is to update the line group to contain only the single member 4545, then just removing <addMembers></addMembers> should do it.
Note: your request shows <member> which should be <members>
AXLSoap - updateLineGroup