There are a few other active ingredients you could try for dandruff (seborrheic dermatitis), if that's what's causing your problem. Keep in mind that it might actually be a different problem, such as eczema or scalp psoriasis. From a quick internet search, the active ingredient in "Dettol Anti-bacterial Soap" is cholroxylenol, is that correct? If so, here are some others you might want to try (i.e. read the product label and look for one of the active ingredients below).
Note, these are "over-the-counter" options only (avaliable without a prescription). A doctor can prescribe other treatments that might not be listed below, or in a stronger formulation than what's available over-the-counter.
pyrithione zinc: usually found in dandruff shampoos like Head & Shoulders; also available in a soap/cleanser form.
selenium sulfide: usually found in dandruff shampoos like Selsun Blue; it's also available in topical forms, but that may require a prescription.
ketoconazole: this is an antifungal ingredient found in anti-dandruff shampoos such as Nizoral shampoo (and generic store-brand equivalents) containing 2% ketoconazole. Stronger formulations are available by prescription.
coal tar: usually found in dandruff shampoos like Neutrogena T-Gel or Denorex; also available in soap form; >> NOTE: this stuff has a strong "unique" smell... make sure you can tolerate the smell before using it. :)
salicylic acid: usually in found in certain facial cleansers (often with the term "oil-free acne cleanser"); it's also found in some dandruff shampoos for "flaky scalp" (like Neutrogena T-Sal), so it's not necessarily just for acne.
You might also consider taking a break from using the Pantene products in contact with your face, and switch to something <<without>> a lot of moisturizers, and not containing silicone (that's usually what the "shine" ingredient is).
This might sound silly, but you could also try "baby shampoo" (fragrance/moisturizer free) for a while, particularly if you're alternating with the medicated shampoos as directed on their label.
One "last resort" option in this case might be to shave your beard (omg!), and see if that helps. You may be reluctant to try that, but remember you can always grow it back later. Howecer, if you do shave the beard and the condition resolves itself, it may be time to rethink the beard. :(
If none of those work, it's probably best to see a doctor about it. They would be able to prescribe something more specific. They may end up prescribing something with one of those ingredients above, but in a higher strength. Alternatively, they might prescribe a topical steroid anti-inflammatory for you to use for a period of time, in case it's not dandruff and is actually something like eczema.
Hope that helps!!
Here's a helpful reference (from the Mayo Clinic website) on seborrheic dermatitis/dandruff. It also includes the topic of facial (beard) dandruff:
More details on "over-the-counter" treatments listed above are included in the section called "home remedies":