Tina,
I'm sorry to hear you have had that frustrating experience. This is not the first I have heard this in the industry surrounding Solo 401(k)'s. I believe I can help provide some education/instruction for you.
If I understand correctly you have a Solo 401(k) and are being told you need to find a new Third Party Administrator/Recordkeeper. With a Solo 401(k), you are not required to maintain a "custodian" unless you are interested in exploring that avenue. There are pros and cons with this, which I will detail below.
The short answer to your question is:
1) You will engage with a new Administrator/Recordkeeper who can perform what is called a "Plan Takeover." I like to describe it as a transplant from one firm to another. All the data, asset holdings, transactions will be ported over to the new recordkeeping system, along with the current plan document being moved and updated as needed.
2) If you currently hold real estate or other asset, you may need to look at retitling, if you elect to move to a custodian. If you are not rolling over to a custodian, but just changing the plan administrator and recordkeeper, you should be able to retain the titling of the investments, which may simplify the process.
3) You should be able to retain the current bank account for the Solo 401(k), but may need to switch to a banking partner that is more compatibly with the Solo 401(k) platform you use.
4) If you have a self-directed brokerage account tied to the Solo 401(k), you may need to make some adjustments there.
PROS of a Solo 401(k) with no Custodian: 1) Freedom of checkbook control, ability to more easily move funds in and out of a bank account in the name of the Solo 401(k). 2) In some cases, lower fees. 3) Ability to more easily link your Solo 401(k) to bank account systems like rental property management systems, or if investing in real estate syndication platforms.
PROS of a Solo 401(k) using a custodian: 1) Should you pass away while Solo is still active, or when you eventually need to terminate the plan and rollover to an IRA, much easier to open an IRA with that same custodian and initiate a rollover of the assets (retitling required at that time). 2) You have a custodian that likely offers some level of client support and education. That said, there are systems for Solo that offer this as well, you just have to find them.
I can appreciate your frustration and have worked with hundreds of investors over the last 20 years navigating the more complex waters with respect to Self-Directed Solo 401(k)s. Unfortunately, the frustration you are presenting is not uncommon from my experience. The good news, there are usually solutions and options for you to explore.
Here to answer questions and help in anyway possible. Thanks!