You can try to set the connection to 4G on your iPhone. To do that, please go to Settings > Mobile Data Options > Voice and Data > 4G.
Please make sure that the area covered is under 4G. You may check the coverage here https://www.webe.com.my/shop/coverage/?pagetype=3g .
You may restart your phone as well and if the issue still persist, please contact webe careline https://www.webe.com.my/explore/contact-us as they will escalate the case to Technical team. Hope this will help you
Please contact Livechat team to get help. If necessary, they'll escalate the case to the technical team to get this fix.