I have been living with an implanted Medtronic interstim device for many years now. This really works well for me. It works like a pacemaker for the bladder.
Before getting the permanent implant I was hooked up with an external trial. After that proved to have a positive effect I was given the "permanent" implant. (They must be replaced about every 5 years or so depending on how fast the internal battery drains.)
The device is about the size of a silver dollar. I requested that it be implanted in my back a few inches above my belt line.
Wires run under the skin to the bladder.
The device has 4 channels loaded that I can tinker with to find what works best for me. Actually, there are 99 potential programs available that the doctor or Medtronic sales rep can change and tweek. I have an external controller that I use to select one of the 4 channels and change their amplitudes. (It works like a Bluetooth device.)
Your doctor may have told you that it may take 2 weeks for you to adjust to a different channel/program. However, I have found that effects of a change are much quicker than that - maybe a day or two.
Make sure you really understand how to operate that remote control. It's easy to accidentally turn off the internal device. (Hopefully, they have improved the interface of the latest devices.)
Higher power settings will quickly drain the battery of the internal device, requiring a new implant sooner. (I had to replace mine after only 18 months. They are supposed to last 5 years.)
If you revisit a previous channel you might get shocked! So, before changing to a different channel I suggest turning the current channel power down. That way when you go back to it later you won't get shocked. Then increase the power slowly from there. Maybe keep notes of what power you were using on a channel before moving to a different one.
My doctor said that the next time I have it replaced there should be an MRI-friendly device available; I sure hope so.
Doctor skills and experience is important. Try to find the best one you can.
God bless you.