I want to replace the Google Dialer and Google Contacts apps. I can disable both in Parameters. If I do it, when I have a phone call, my phone rings but no screen activation and no phone app (dialer or other) displays: I can't answer. Then I have a notification of missed call transmitted from the Call Manager system app and sometimes a sms (but I think this last is a service provided from my phone provider).
Talking about Call Manager system app (and Phone Services system app too), I activated all I could (all notifications, all authorizations, etc...) but nothing changed the problem.
I tried Simple Contacts, OpenContacts from F-droid and Asus Dialer & Contacts from APK pure (previous version since the last don't start on my phone).
If Google Dialer is disabled I can't phone, if Google Dialer is enabled and (Simple Contacts or Asus Dialer&Contacts) is the default app for phone, I can receive calls but it's the Google Dialer which displays.
Please help!!!

nota: maybe a rom without gapps (Google Apps) could resolve this problem?
nota 2: I know how to flash my phone with spflashtool
nota 3: my firmware is 2018092919_s32v63c2k_jk_pro .rar from viewtopic.php?t=480235#p795494 (noticed as verified).
Other link: https://naijarom.com/blackview-bv9500-pro , which corresponds to the BV_BV9500Pro_V1.0_20180829 .rar from the first link (sha512sum comparison of all uncompressed files verified by me) but not specified as 'verified', that's why i use the second from the first link (the *jk* one)
nota 4: Google's Messages can be replaced with Silence from F-Droid (latest stable version, not the unstable one) and is perfectly working
Thank you all for reading me and maybe for help you could give
Bests Regards / Cheers everyone
