"Your device only supports the "Dual Standby, One Active" feature, which means that you cannot use both SIM cards simultaneously for calls or data services. "
More details:
See pages 14 and 15
HUAWEI P smart 2019 Quick Start Guide(POT-LX1,EMUI9.0.1_01,EN,Dual) [ 4.7M ]
http://consumer-tkb.huawei.com/ccpgw/msa/TKB/app_0000000000011227-CcpTKBKnowOut/ctkbknowout/servlet/show/knowAttachmentServlet?knowId=fr-fr00693302
See pages 24 and 25 (including the Information "Some operators may not support this feature")
Dialing
Activate call forwarding so you don't miss any more calls
HUAWEI P smart 2019 User Guide(POT-LX1,EMUI9.0.1_01,EN) [ 10.4M ]
http://consumer-tkb.huawei.com/ccpgw/msa/TKB/app_0000000000011227-CcpTKBKnowOut/ctkbknowout/servlet/show/knowAttachmentServlet?knowId=fr-fr00689333
Both pdf documents can be accessed via :
HUAWEI P smart 2019
P smart 2019 Dual SIM 3GB + 64GB (POT-LX1)
https://consumer.huawei.com/fr/support/phones/p-smart-2019/