Is ARM One a Legitimate Investment Platform for Mutual Funds and Savings?

Yes, ARM One by ARM Investment Managers is a real Nigerian investment platform operated by Asset & Resource Management Company, and they state that they are SEC-regulated.
However, what you are describing is a serious operational issue that should not be ignored:
withdrawal not delivering,
a wrong bank account appearing,
inability to change account details.
That does not automatically mean the platform itself is fraudulent, but it does mean either:
your account details may have been wrongly linked,
your profile/KYC may be incomplete or corrupted,
there may be a system glitch,
or, in the worst case, unauthorized access to your account.
There are also recent public complaints from users about delayed withdrawals, account activation issues, and poor customer support on the ARM One app reviews.
What you should do immediately:
Stop making further deposits for now.
Check whether the bank account shown is:
partially masked,
an old account,
or completely unfamiliar.
Change your password immediately and enable 2FA if available.
Contact ARM directly through official channels only:
Email: enquiries@arm.com.ng
Phone: 02013305005
Send them:
screenshot of the wrong account,
your registered phone/email,
proof of ownership of your correct bank account,
and request:
immediate freeze of withdrawals,
correction of bank details,
and confirmation of your account integrity.
If they do not resolve it within a reasonable time, escalate to:
Nigeria SEC complaints portal
and possibly the Economic and Financial Crimes Commission if unauthorized diversion is suspected.
One important distinction: There are unrelated platforms online using names like “Arm Trade” that have scam allegations and withdrawal complaints. That is different from ARM One by ARM Investment Managers.
Your situation currently looks more like an account or withdrawal-processing problem than a confirmed scam, but you should treat it urgently until your withdrawal is successfully received.